The 47-year-old is currently home with his family in Invercargill - Chilean rugby seasons run from March to November - but will return next year. During term time, he generally does six-week stints before returning home for a week or two.
Henderson says the four teams he runs lost one game in about 85 last season. Each team won its grade and, while the strength of Chilean rugby might not be renowned, most teams he administered were lagging upon his 2010 arrival. The wins included a number in Argentina and, in the case of his under-16 grade, a win over a touring side from Brisbane.
"My job is to raise the standard of rugby at the school and club by coaching the coaches. It takes time to bed in your ideas, for people to understand what you want and to have faith but I've had unbelievable support from my employers.
"Chilean rugby fans tend to be huge All Blacks fans. In fact, they now call New Zealand 'champions of the world' rather than 'world champions' which I think has a better ring to it.
"Fortunately things have worked out for me on the basis of our results. Sponsorship is going through the roof, player numbers are up 40 per cent [since Henderson's arrival] and the players have embraced a professional attitude."
The club and school are largely bilingual but Henderson has work to do practising his espanol.
"I can order a beer and a steak fluently and give directions to taxi drivers. I have a bit of conversational stuff going on but they speak pretty quickly so it's difficult for an old gringo to pick much up."
Henderson originally received the Chilean offer by chance.
"My neighbour Tom Downey is a rugby agent. He rocked over one day and asked whether I enjoyed touring Argentina in 1991. I played seven of the nine games and made my test debut on that tour because Jonesy [Michael Jones] pulled a hamstring early on. I loved it. So I went across in November 2009 for an interview.
"They liked my message. I learnt a lot of lessons in first class rugby and feel well qualified on such matters having spent so many years working out how to beat people."
Henderson jokes it might surprise some past team-mates but he has been putting in more than a full day's work.
"Some days, I start meetings at 8am and finish my day at 11pm. They won't believe that ... but it's true. I've been misread for so many years on that [my work ethic]."
Henderson is also helping top Chilean players make the step up.
He had a word to Downey which resulted in deals being arranged to see the 2m, 115kg lock Pablo Huete play for Tasman in this year's ITM Cup. A European passport has since seen Huete secure a contract with French club Castres. However, players such as Huete tend to be the exception.
"Our eight-month season means it's hard to keep up the intensity," Henderson says. "We don't have many players who are 28 years and older. There comes a time when girlfriends and wives start having a quiet word in the background because it's quite a commitment.
"It means players don't spend enough time becoming better, more knowledgeable athletes."
Chile has made progress on the international front.
This season, they beat Brazil, Paraguay and Uruguay - for the first time in nine years - but lost 61-6 to Argentina.