Camilla particularly thought this was a neat idea, commenting to staff that it's a beautiful way to remember her beloved pet.
The penultimate part of the tour saw Arthur the 3-legged dog get washed while the Duchess watched.
She put a token into the machine to begin the wash but failed the first time. But it was all go once it started working.
The wash was quick and Arthur was very well behaved.
SPCA volunteers say Arthur who lost a limb when a car ran him over was picked because he was a good dog who didn't fear crowds.
The whirlwind visit ended with Her Royal Highness meeting board members and volunteers and chatting to them over a strong cup of English Breakfast tea.
One board member, Charlotte Fisher had the privilege of talking to the Duchess. She says they talked about horses for much of the time. Ms Fisher says the Duchess came across extremely sincere and friendly.
Patron of the the SPCA, Former Mayor Kerry Prendergast farewelled the Duchess and gave her a gift, a New Zealand branded Swandri coat for her Jack Russell Beth.
The Duchess said "I'm sure Beth would be very pleased - I'll take it back home and she will be all ready to face a long winter."
Meanwhile, Prince Charles was the toast of Westport. So much so, he toasted the town back.
The heir to the British throne shook hands with a good many of the Buller town's population during his walk-through of the main street.
"He asked what school I went to and is this my brother and then we shook hands," eight-year-old Sheldon Walsh said, after his royal encounter.
Sheldon said he was too busy fielding the prince's questions to snap a selfie with the guest of honour.
Buller High School prefect Emily McDonnell had the same problem as she and the school's head boy, Tony Carleton, showed the prince plant boxes pupils had built for display in the town centre.
It was left to their friends in the crowd to capture the moment for them.
"We had a few strategically placed people," McDonnell said.
Peter Hart, of Reefton, arrived in town nearly three hours ahead of the prince's visit to claim a good vantage point for a meeting. It paid off, but his Union Jack banner - captioned "Proud to be a Pommie Bastard" - probably did more to catch Charles' eye.
"He said, 'You're not the only one," Hart said.
Having charmed the crowds, Charles visited the West Coast Brewery for some beer (the organic brew piqued his interest) and whitebait patties. He turned to the expectant crowd watching his every move and declared the lager and pattie a perfect match.
"Here's to Westport," he said.
Prince Charles and the newly-minted head of the New Zealand Defence Force also visited the headquarters of Exercise Southern Katipo in Westport.
The prince, his considerable entourage and media descended on the operation's base to meet them men and women involved, inspect a hospital ward and examine various tools for dismantling and disposing of explosives.
Charles, visibly impressed, was conscious of his imposition.
"I can only apologise if I've caused mammoth disruption," he said.
The prince reminisced on his own time in the military 40 years ago, a "small cog" in an exercise somewhere and not always with a view of the big picture.
"I hope the wash up at the end reveals some interesting points," he said.
"But whatever the case, you can always blame me if it goes wrong. I'm bound to have caused some awful hold-up just at the crucial moment."
Exercise Southern Katipo, based in a fictitious Pacific island split in two by political unrest, involves more than 2000 army, naval and airforce personnel and runs until the end of the month.
Eight countries - Australia, Canada, Fiji, France, Papua New Guinea, Tonga, the United States and the United Kingdom - are taking part.
Charles thanked them for their service, "so often unsung and unseen".
"One of the reasons I've been trying to go on about climate change for so long is unfortunately it's a threat multiplied. I'm glad to see that at last various military people are taking this seriously," he added.
"I've always felt the threat is going to come more from mass migration, conflict over scarce resources, sea level rise, droughts. The fact that your practising all this is obviously going to be of enormous importance."
Locals had mixed feelings on the royal visit - Westport's first since the Queen's stop during her coronation tour in 1953.
"I would had loved to have seen Prince Charles," the woman at the Westport New World supermarket checkout said.
"The town's buzzing. I wish I wasn't working."
Staff at the cafe across Palmerston St were less enthused. None were planning to make the short walk to the royal route for a glimpse of the future king.
Before her visit to the SPCA, inmates at Arohata Womens Prison welcomed the Duchess of Cornwall with song.
Dressed in a blue coat sporting pearls and a Remembrance Day poppy brooch the Duchess was treated to a performance from the prison's kapa haka group.
She was then led through the long prison hall past the holding cells to be shown some of Arohata's rehabilitation initiatives.
Camilla is no stranger to life behind prison walls.
She is the Royal Patron for The Friends of Erlestoke Prison in Britain.
The charity promotes and supports the rehabilitation of prisoners.
She has met prisoners taking part in schemes to improve their literacy levels and inspected prison grounds and programmes.
At Arohata she was shown the prison's literacy program and new online learning facilities.
Students told the Duchess they wanted to finish high school and go to university.
Camilla's love of literature was evident as several prisoners from the creative writing course shared their work.
"I didn't bring my specs so you will have to read it for me," she said.
She met with prisoners undertaking the drug and alcohol treatment programme.
The programme is the only one for women prisoners in the country.
The Duchess showed genuine interest in how the programme was helping the women.
"How long have you been in the programme? What are your ambitions after leaving prison?" Were some of the questions she put to prisoners.
"I want to return home a great mother to my kids," was a response.
Camilla was presented with a framed quilt handmade by prisoners and decorated with Kiwiana icons.
Department of Corrections deputy chief executive Christine Stevenson said it was an honour to have the Duchess pay a visit to Arohata Prison.
"The Duchess is a supporter of literature programs within prisons and was very interested to see the programme in Arohata," Stevenson said.
The women on the drug treatment programme shared their journey with the Duchess, she said.
They were "beyond excited" to have a royal visitor.
Earlier in the day, Prince Charles and the Duchess of Cornwall ended a whistlestop visit to Nelson and Tasman.
The royal couple managed a public walkabout, a visit to Nelson's Cawthron Institute and World of WearableArt gallery, and a food and wine event in the four hours they were in the region, which turned on its warmest charm for the first royal visit to the region since 1986.
A food and wine event at the Mahana Vineyard and Winery in the verdant Moutere hills, saw the Royal couple chatting easily with some of the region's top wine, cheese and seafood producers.
Winery owner Glenn Schaeffer, a retired Las Vegas casino executive, philanthropist and major supporter of the arts in New Zealand, said it was a huge honour hosting the Royal couple.
"There's something about the monarchy that stands above all else. To have the future King of England here, and the Duchess - it's just a tremendous honour for us," Mr Schaeffer said.
Mahana grows mainly pinot noir, with some pinot gris, Riesling and chardonnay grapes and achieved full organic certification in 2011.
The gravity-fed winery is built on four levels, to reduce the use of pumps. Power is also saved by using insulated wine tanks and a precisely managed temperature control system. Prince Charles appeared to enjoy a lengthy chat with winemaker Michael Glover as the Royal party, escorted by Mr Schaeffer and his fiancee Chandler Parker, descended the winery's multiple levels to the food and wine event in the lower cellar.
Judy Finn of nearby Neudorf Vineyards, had a long chat with Camilla, the Duchess of Cornwall who is President of the United Kingdom Vineyards Association.
Mrs Finn said she congratulated the Duchess on the increasing strength of English wines.
"They've just won a taste-off between the French - between Champagne and English sparkling wine, which they won and that's what I said congratulations for. It's a real mark for the future of English wine. They're very, very good."
Mrs Finn said the Duchess was easy to talk to, and Nelson had shown itself off in top form.
The Source to Serve Nelson-Tasman food and wine event in the Mahana Winery cellar was also a celebration of the region's high quality seafood and cheese products, which were set up at various stations their Royal Highnesses were escorted around.
New Zealand King Salmon board member Paul Steere said it was a "brilliant day". He said Prince Charles, as president of the Salmon Anglers' Association, was particularly interested in New Zealand salmon farming operations which were different to those in Scotland.
"He did suggest they might try the same later on," Mr Steere said.
Minister for the Environment and Minister for Building and Housing Nick Smith said he and Prince Charles discussed matters around conservation and housing.
"He recognised we had challenges in the area of housing and shared some of the Living Communities work that his own trust has been doing, and I'm very keen to follow up on some of the challenge of how do you build intense urban communities that actually work, and he's a big fan of that.
"I also acknowledged that Prince Charles has shown a lot of leadership in the area of challenging countries to do better around marine conservation."
Dr Smith said Prince Charles acknowledged the need for countries to work harder at doing a better job of high seas management.
Prince Charles was then whisked away for a flight to Westport while Camilla returned Wellington for several engagements.
