PNG coach Jason Demetriou used Nene Macdonald in the second row for Friday's international in Wollongong, a new position for the 32-year-old.
"It was a massive change. I've never played there before, and I was blowing for a bit, trying to get used to it."
"I got the hang of it in the second half. I like that position. It was pretty sick."
Macdonald and St Helens mutually ended their arrangement on Tuesday, leaving him a free agent after six years away from the NRL.
He said he was ready to return and hopes to join the PNG Chiefs when they enter the competition in 2028.
"I'm lacing the boots up, straight away," Macdonald said of a possible Chiefs offer.
"It's always been a dream of mine to have an NRL team in PNG, and now it's actually coming true."
Macdonald, born in Port Moresby, wants to join Kumuls teammates Alex Johnston, Gairo Voro, Morea Morea and Finley Glare as a foundation Chief.
He has played 23 Tests and is the Kumuls' all-time leading try-scorer, while ranking just behind close friend Rhyse Martin for most appearances.