"It takes a lot of study and preparation," Hartley told Radio Sport. "Before going to Austin, I had a 50-page manual to memorise. Even to start the car is a complicated process.
"The driver manual is just one point. It is kind of never-ending. At the track, it is just one meeting after another.
"There are a lot of points that are very crucial and then a lot of it comes down to feeling - feeling the car with your backside. That is the main role of the driver - feeling the car underneath you. To make that car work as quick as possible from all those cues you get and sensations from your body - that takes years of experience. That is what I have been working towards all my life.
"All those little movements and feelings and sounds and then using those to put the right foot down or give it the jandal as Scott [McLaughlin] said."
A 13th placing on debut exceeded the expectations of many and he was widely praised for how he performed on such short notice.
At 27, Hartley felt he was in a better space to cope with the task but it certainly didn't mean things were easy.
