Overcoming car issues earlier in the weekend, the 23-year-old climbed from P7 to P2 in Race 5, only led by championship leader Shane van Gisbergen.
Now occupying a full-time role for Erebus Motorsport this season, Kostecki says he is focused on speeding his progress as much as possible.
“I spend all of my spare time at Norwell Motorplex,” Kostecki told Supercars.com.
“I’m always out there, trying to help a young bloke or training myself; I’m still pretty young and I try to learn off of people as much as I can.
“As much as I can fast-track that learning curve going through my rookie season, that’s all I want to do.”
Originally from Perth, Kostecki spent time in the States as a teenager racing in a NASCAR development series, before returning home and following the Supercars pathway.
In recent years, Kostecki has been mentored by 2014 Bathurst winner and Norwell Motorplex owner Paul Morris, who has coached several young drivers including Shell V-Power Racing Team recruit Anton De Pasquale.
The young Erebus star attributes his growth to having Morris’ support and guidance.
“I try to surround myself with good people most of the time, and whether it’s at Norwell or whether I’m spending time with the team,” Kostecki said.
“Understanding what you need to work on is probably the hardest thing being a race car driver.
“Recognising where your weak points are is why I have Paul and others around me to help me and guide me through those tricky parts of life.
“Paul pulls me into line when I’m doing something silly or stupid, he’s always sending me texts throughout the race weekend or if he’s at the race weekend, he’s always in my corner.”
Grateful for Murphy’s praise of his wet-weather skills, Kostecki admitted it was hard to pinpoint when his finesse for wet conditions came from.
“That’s really awesome for Murph to say,” he said.
“I’ve always been fast when it rained in go-karting growing up as a kid.”
“Anytime it rains in Queensland, I’ll be down here at Norwell running laps in the rain, trying to understand how to navigate through it and understand how to make myself better when it does rain."
“In the rain, you need to be on your game, so I spent a lot of time here at Norwell; it’s kind of my home really.”
Kostecki heads to next month’s trip to Symmons Plains 10th in the standings, with Erebus teammate Will Brown 15th.
The Repco Supercars Championship field will return to Symmons Plains for the Beaurepaires Tasmania SuperSprint across April 17-18
The event will be broadcast live on Foxtel and will be streamed on Kayo.