Mr Mahupuku, who was dragged from the blaze by other firefighters, suffered serious burns to 33 per cent of his body, mainly his arms and back.
He has since undergone two skin grafts for burns on his back and three other surgical procedures since being flown to Middlemore.
He said he was "blown away" by all the messages of support and assistance he was getting from people around the country.
"Everyone has been amazing. I have been getting a lot of support. Cards and messages have come from the public who heard what had happened," he said.
"There have been lots of messages from firefighters from around the country and lots of visitors."
Colleagues have rallied around their injured mate, with firefighters from around the country visiting him.
Mr Mahupuku said he was able to get out of bed and was taking steps forward in his recovery.
"I was in quite a bit of pain at the start, but it's minimal now and I am on good pain management."
Fire Service region manager, Assistant National Commander Ian Pickard said the service was doing everything it could for Mr Mahupuku and his family and wished him a speedy recovery.
Meanwhile, a full operational review of the incident was underway and was expected to be completed within a few months.
The probable cause of the fire had been identified as an exothermic reaction between the chemicals being used in the process to manufacture racing car seats.