For those students that fight the over the top move, I like them to feel that dropping or dead fall of the hands straight down vs the cast move. I will have a student stand with his or her back to a wall about 3 or 4 feet away, get in golf set up position, take club to top of swing and have the golf club head touch the wall. I will tell student to start the downswing but must keep club head against wall. This will produce a dropping feel making the student learn to rotate through impact, keep club head behind hands creating lag, and start to attack ball from the inside position.
I will record this drill for them so they can practice at home. After about 5 minutes I will then have the student hit a shot reproducing that dropping feel. I use TrackMan and 2 cameras down the line and face on to record the swing, I will pull up the first swing and then pull up the swing after the drill and do a comparison. The student sees immediate change and how to continue to improve.