I do hunters, as well as eventing, and I don't teach changes over a pole or through the trot.
I school lots of counter canter and I also school cantering down the diagonal or center line and doing a transition down to walk. This way when I canter down the center line or diagonal, my horse will think "whats next".
I have been doing an exercise a lot lately where I canter down the center line and make sure my horse is very straight. Then BEFORE the end, not during the turn!, I ask for the change. Not only do you have to think about keeping the horse straight, you have to think about keeping you straight. If my horse is not straight I do a walk transition and back up to canter immediately.
Gypsy & Scout <3Everybody is a genius. But if you judge a fish by its ability to climb a tree it will live its whole life believing that it is stupid. ~Albert Einstein