One thing that is helpful with regard to grid starts: I've read and it seems entirely true, that when you have any % of brake applied... the car absolutely will not launch. It's different than real life in that regard, so it's really safe to just conduct a launch start (A) with 60% throttle or so (more is just slamming the TCS dithering and taking away from a faster start, for most cars) and (B) foot on the brake, at any moderate pressure, and then release the brake pedal at the 'lights out'. Be sure to be ready to shift up, and there is little else to manage for an optimum start in most cases. I put the TCS on 2 (or 3 in extreme cases for high-HP, low traction RWD cars, but not really recommended as it will slow your upshifts) to avoid wheelspin, then flip it to my usual 0 after the first turn or next available chance.
You can practice it in the lobbies, as noted, but it's not too difficult once you realize the brake pedal is 'magic' and there is little to manage other than lifting off that pedal when the lights go out!