Players serve to their partner - the partners catch the balls and serve it back to their partners. Continue for 10 serves each. After 10 serves, each player backs up 10-feet and repeats 10 more serves. After 10 more serves, each player backs up to the endline and repeats 10 more partner serves. Instead of simply catching the serve, have each player pass the serve up to herself, catch it and then serve it back.
Setters work on repetition of any particular set.
Work fast, Coach, once learned. Drill stops and rotations are made only when the group on the court scores 12 points with full coverage. Coach stands at net but off-court. That's 6 players involved in drill. The three players involved in the action move off-court and the other 3 move on for the second attempt.