I’ve done something that’s very simple and cheap that I learned from my old boss Craig Welty. I use a pool noodle and put a piece of pvc pipe in one of the ends. I stand down the line behind the student just inside of the golf ball to the target and have them swing under it without touching while they are hitting shots. This helps them to feel what they should feel instead of me just showing or telling from video analysis etc. This gives them immediate feedback when they go to an old habit such as, over the top, without hurting them, yourself or the golf club. Sorry for the crude description, but it’s a lot easier to show!