When I'm trying to change a kids mechanics (hitting, fielding, pitching) I usually go through a progression of speeds so the player can feel the positions of the desired mechanics. Usually I start the skill at 50% speed, then 70%, and finish at 90%. At 50% and 70% the player should be able to feel it. I tell my kids to "concentrate/think about" feeling it in practice, so it becomes so natural they don't have to think about it in a game. In the game I want them competing, not thinking about the movements.
I've also seen golf instructors use this method too.
I've also seen golf instructors use this method too.