Each time you introduce a new move, your horse is building on past maneuvers.
Introduce new exercises in baby steps. Break them down into small pieces, and teach him one piece at a time. If he gets confused or you hit a roadblock, back up to the last step he mastered well and practice it again – ending each exercise with a familiar and well-polished exercise. ie: If you want him to disengage his front, accept one step over at first. When that is accomplished consistently, ask for two steps, then ask for three, then ask for a complete circle. Accept small victories until you have the entire multi-step maneuver accomplished.
Learn about Signal time. Give him ample aids and lead up to the maneuver consistently and slowly, building from “anticipate” to “request” to “demand”. Each maneuver cue starts with a subtle action such as just picking up the reins. Then moves to a change in your position in the saddle (lean forward). Then adds verbal “cluck”. Then moves to leg pressure (clamp thighs), then moves to demanding leg (spur).
Build the routine of your cues first. He will anticipate your request based on the sequence and begin to act at an earlier and earlier stage of the routine until the cues are so subtle no one can even see them.
Notice that the rider MUST be trained before the horse is trained. If you cannot master the cue sequences, the horse will never master the lesson.
The same rule applies to changing equipment. Change only one portion or attribute at a time.
If you are introducing a new bit, keep as many parts of the old bit mechanism in the new bit with only one change. ie: if you want to introduce your horse to leverage, choose a bit that is exactly like his old bit but with small cheeks. Don’t go from conventional snaffle bit to a conventional curb bit in one step. Keep the two-piece mouthpiece and add small shanks such as a Kimberwick bit or Pelham. Then change to a longer shank but with same mouthpiece. Then change to a different mouth with same configuration of cheeks etc. etc.
This bit-changing sequence requires more bits during his trainng, but will make transitions easier and faster.