Do lots of groundpoles. After you can control his stride then lunge him over a small jump a couple of times and even if he just trots over it its okay. Eventually move him up into a higher jump and put him in what most people I know call a "shoot". Line up a jump perpendicular to a wall and parrallel to the wall set up some high poles so it's like a hallway that he goes through and over the jump, then freelunge him over the jump, drive his motion forward as he approaches the jump and he will eventually move up from trotting over it (or plowing through it) to picking up just the back feet and trotting with the front, to Finally picking up all feet. It might take some time but he will get it eventually.