He earned a meritorious second place in a Ford Focus and said the drive helped to clear his head for a return to Supercars.
"It was good to get rid of that memory," he said.
"You're only as good as your last race and my last race we did well. And it's never a bad time to race at Bathurst.
"The Supercars races these days, every lap is a qualifier.
"You make one little mistake in tricky conditions and instead of dropping one place you drop six or seven.
"We'll be making sure not to repeat that on Phillip Island."
The man to beat at the Victorian coastal circuit is McLaughlin, now in the red-hot Falcon.
The Kiwi scooped the meet last year and earned four wins across the last eight races in Volvos for Garry Rogers Motorsport.
The arrival of DJT Team Penske has shaken up the natural order, perhaps placing the upstarts ahead of their more established rivals.
But Mostert and teammate Mark Winterbottom are having none of it.
"We're not in the shadow of anyone. We're our own team," he said. "There's a lot of focus going on what people call Goliath teams fighting out for the championship but we're definitely in the mix with the improvements we've made.
"We'll keep going under that radar. It's where we like to be."