Currently the boss of Scottish club Glasgow Warriors, Rennie has agreed a three-and-a-half-year deal as Australia's new head coach and will join the Wallabies at the end of the current UK season.
"I've got a bit of work to do from an Australian perspective," said Rennie, who was appointed in the wake of Michael Chieka's departure following the Wallabies' World Cup quarter-final exit.
"We're sorting out staff, not just coaches but the whole staffing group, and it's an extensive review.
"I can get my Glasgow work done, and then at 10pm (local time) jump on Skype and have a chat with the guys who are driving it on the grass.
"It makes you busy, but it doesn't detract from my focus and my primary role."
Rennie says he is not a big sleeper - "five or six hours is plenty" - and is used to working across different time zones due to his move from the New Zealand-based Chiefs to Glasgow in 2017.
The 56-year-old former New Zealand U20 coach, is also planning to visit Australia in the new year to acquaint himself further with his new role.
"We do get a break at the start of Six Nations when I'll spend a couple of weeks in Australia," Rennie said at the Guinness PRO14 league's media day in Cardiff.
"I'll be meeting some people and getting around Super Rugby and making strong connections.
"I'm comfortable I can make that happen. It was important to me that I complete my contract here.
"I made a commitment and want to see that out. Australia have been great in that regard to allow me to do that."
Attack coach Scott Wisemantel, who this week left the England set-up, is expected to join the Australia coaching staff.
"I'm not convinced he's signed, so I won't comment," Rennie said.
"But it'll be great to have him on board. He's high quality."