The only way your darling knows he got right answer is if you stop the tap immediately when he moves the distance and direction you want him to do.
Once, he has it down on one hip side, start on other hip side from the ground.
Once he has that down, start teaching it while you are up on the saddle (this is fun). When he learns it under saddle, you can get him to wiggle his happy little butt side to side like there is no tomorrrow. And, he'll be so proud of himself !
Mary Dixon Adventure Horse Riding in NYS RideNYS.com