Canter poles up to a fence with grids and bounces get him sitting on his hind legs.
Place ground poles before and after fences and make him halt when he gets too fast.
Halt him before and after the jump
My horse was like that so my coach said if u keep your hands down and stop at random times. Also do heaps of sit trot and get the horse working from behind so it can carry its self in front. And in the canter do a big circle and gradually move in to a 10m circle then move back out and keep doing this until your horse has a steady canter. If your horse is doing that we'll go straight for while and if they speed up do the circle
I had this problem with so many of the previous horses I’ve owned. As soon as you feel them rush halt before and after the fence just lean back slightly and ask them nicely first and harder and harder each time until they stop, they will soon get the hang of it and start to slow down. Hope this helps :) x
Place canter poles in front of the jump or lower the jumps and make him trot/walk in