I've thought several times how to attach a fine sandpaper disc on the side/toward the front of the pitcher's leg just below the hip bone (wherever the hand would pass by on a pitch), and another piece of sandpaper on the side of the hand just below the pinky. If they are keeping that hand in close to the body like they should, the sandpaper pieces make contact, giving a nice audible "shhhp!" to reinforce they did it right.
Haven't pursued it any further, yet. Maybe a snug leather glove with four fingers cut off can substitute for sandpaper on the hand.
Haven't pursued it any further, yet. Maybe a snug leather glove with four fingers cut off can substitute for sandpaper on the hand.