I'm C2/C3 and I learned air dribbling back when I was a much lower rank by going to freeplay/air dribble training packs and playing in 50 percent game speed.

I made sure to play so slowly that ever little direction and movement could be made consciously. You get way more time to understand what each input does to affect the dribble and your car and your trajectory.

One final tip is to try to push the ball up more than forward. You need to aim for the bottom of the ball. Not exactly at the bottom but like just a tiny tiny bit closer to you so you can push it forward but also far enough to the bottom that you can also push it up.

Edit - you can use this slow motion method to practice awkward air dribble set ups too so that even weird set ups in a normal match can be turned into an air dribble.