Filming girls on Slo Mo feature of your phone and playing it back to them real time is a great tool.
You'll get to where you can slide with your thumb to the exact frame you need. Then play, thumb slide it back, play again. There are times we do this after every pitch or every at bat and discuss what we're working on.
It’s great! A friend did it for me the other day and I’m actually pitching better than I thought. (I’m just playing social) It’s a wonderful tool.