The steering was controlled via left stick, tricks/stunts by moving the right. Triggers were acceleration/braking as expected.
Can't remember what the bumpers did (if anything), sorry!
The champion creator did take a little while (I do forgive Kinect for that, it was loud, dark and generally a poor environment to scan me in), but it was interesting to watch. First the Kinect asks you to raise your hand above your head to show who wants to be scanned. Then you step back, and it creates a digital you out of blocks. Then it asks you to step closer, and the blocks change into a real time scan of your face. It was pretty amazing to be honest, you could see all the muscles change when I spoke, laughed, frowned etc. Then it asked me to turn my head to the left, right, tilt up and down. Then it made me my Champion. Overall, around 5 minutes of waiting though. But test build blah blah blah.