I used to teach all my horses to turn on the forehand. Something was going wrong if the rider needed to pull so hard that the snaffle was pulled through her horse's mouth.
Really all you do is stop your horse in place and ask him to move his hindquarters around his front feet. It's easy to teach and there is not much rein action. Oh - and you teach it one step at a time. I would ask for one step then immediately ask the horse to move forward. Nancy
