Not an expert, just a bucket dad with a sample of one, but when DD made the switch, we played underhanded catch and the natural motion just started happening. The whip from IR wasn't perfect, but the body naturally pulled the arm into the body to start creating IR. The hand naturally turned from pushing the ball down to more of a pull down. I had to tell the DD that we are not pitching, just throw the ball the way that feels natural. Forget the HE finish, just throw the ball into the glove. It created an easy starting point to relearn pitching.
It's amazing what happens when we get out of the way of the natural motions of our body.
It's amazing what happens when we get out of the way of the natural motions of our body.