The 'Ikale Tahi could only manage one win over Canada in the last of their three games at the recent Pacific Nations Cup but have three more warm up matches before the world showcase.
Kefu said after a month of training and touring together his players were in good shape.
"We've made some big shifts in terms of weight loss and body fat loss. We also made some huge shifts in terms of intensive running," Kefu said.
"It was important that we get a win considering the last four weeks of training have been pretty tough on the boys."
The win also demonstrated to players the viability of their coaches' game plan.
"We think we've got a way to play the game that will get us some positive results," Kefu said. "The players are starting to buy into that. It's all about spending time together and working on those things that will get us the wins."
The 'Ikale Tahi are now enjoying a week long break before reassembling in Tonga this weekend ahead of their warm-up game against the Western Force.
Kefu said the match was a rare opportunity for his team to play at home.
"That's the main reason why we're doing it, just to give something back to our supporters and our fans back in Tonga. We wanted to bring a game to them, we wanted to reconnect with them.
"Hopefully we can have a win and they can see us off on a positive note towards the World Cup."
Test matches against Fiji in Auckland on 31 August and New Zealand in Hamilton on 7 September complete the 'Ikale Tahi's World Cup build up.
Kefu said he was close to settling on his 31 man World Cup squad.
"We've got a squad of 32 reassembling in Tonga... so we've kind of got our heads around who we want to pick we've just got a few loose ends."
Those include the injured captain Nasi Manu, whose recovery from testicular cancer to be named in Tonga's Pacific Nations Cup team made headlines world-wide.
"Everyone has come through the four weeks pretty good except for Nasi but we're confident he'll get through his rehab and join us in New Zealand," Kefu said.