Mrs Rushbrook's design had been picked from a number of submissions by local artists.
The finished design features two children looking into The Crossing stream, a tui flying overhead and a bird's nest, which will be painted on the top of the box.
"There's the day-care centre up the road so hence the children, and there's the native bird because there's a number of tui around, and then the stream."
The artist of 20 years has been at the box everyday this week but said the sun had been too hot and was drying out her paintbrush, forcing her to wrap up by mid-afternoon.
Mrs Rushbrook expects her mural to be finished around the end of next week.
She also has murals on cabinets in Cornwall St and Hillcrest St, which are coated in anti-graffiti paint to deter vandals.
"The residents committee requested this box be done because it gets targeted with graffiti a lot," Mrs Rushbrook said.
The artistic initiative by Chorus aims to detract people from vandalising their cabinets.
Chorus had tested out the theory in Auckland and it had been a success, with decorated boxes not tagged, Mrs Rushbrook said.
"It's nice how it's making a difference in the community.
"It's positive, it's interesting and it's getting the community involved."
"I get a lot of interest. People pop along to talk and look, and I think they're enjoying watching it come along."