Teach the body to be comfortable with the proper strokes.
I'm about training body movements - "Kinesthetic learning." If there is a problem with a stroke I help the student get used to the right feeling.
I'm sure sometimes when posters see my advice to crack a whip, use a rope, use a baseball bat, chop a log, hold a glass of water, etc. they don't take me seriously, but these tips absolutely do work. I will ask the student to overemphasize parts of a stroke to get the feeling of the proper stroke.
I also keep a constant running dialog in a lesson for auditory learners (though not a step by step breakdown of every little thing) and visually demonstrate everything for visual learners. However, since you want the body to do something, you must physically train the body. Sometimes it drives me nuts to hear everyone having nit-picky debates on pronation, supination, etc. These don't really help someone learn things on a tennis court.