thanks for the advice! (: but, sending him off is my very last resort. He has a wonderful, rounded jump, a beautiful extended stride, and knows how to do it all. He just needs to get his head right.
sorry if I wasn't too clear, but i'm looking for exercises to solve the anticipation of transitions, speed, and general under-saddle hotness that he and I can work on together.
Oh, ok. In that case I agree with what MIE said. Start from the beginning. I have an OTTB who has a tendency to get hot. We had progressed all the way to jumping courses. But I decided that she wasn't learning very well because of her hotness. And I'm pretty sure that she was getting hot not only because of her predisposition to it but also because I was pushing her to fast.
So I backed up about 20 miles and just focused on walk/trot work with her. I spent a good long time walking her. Our main focus was on bending in the corners and staying straight on the sides. I held my reins close to the buckle and used light rein aids and alot of inside leg to get her into the corners. Then we do lots of circles all over the arena using mostly leg to keep her from falling in or out. Once we had done that in both directions we'd do figure 8's. Again use light rein aids and alot of inside leg when bending.
After doing that at the walk, do the exact same thing at the trot. You may need to shorten your reins a bit. But try to keep it to a minimum. Try to slow down your posting instead of asking with your hands if you need to slow your horse down. Work on bending and circles in both directions and then do some figure 8's. He may not bend as well as he did in the walk. That's ok, he just needs time to get supple and responsive to your leg.
After trot work I like to work on walk halt transitions. This gets your horse thinking about slowing down a bit after trot work. Keep as much slack in your reins as possible, give a loud, clear ho or whoa. Then gently increase rein pressure until he stops.
After that I like to work on walk trot and trot walk transitions. Again use ho or whoa in the downward transition.
Then we work on backing and then end the session with what we started with. Walking around the arena and bending. However if your horse doesn't understand or gets frustrated with bending, just walk on a loose rein until he understands what your asking him for. Always end with something he knows how to do.
Now, don't immediatly progress to canter. Spend a few days or maybe even a week just doing walk trot work. You don't want your horse thinking that every time he goes into the arena he'll get to bomb around at a canter or gallop. The walk/trot work will help get that into his head. You may even have to revisit it later in his training.
When you are ready to canter to walk canter or if it's easier, trot canter transitions. Always ask for canter in a different spot in the arena so he doesn't anticipate and start to get hot. Canter for a few sides or down one side of the arena and then ask for a downward transition to a walk. This is where the walk/halt lessons will become handy. Say ho or whoa and use gentle rein pressure until he walks. Then walk around the arena a couple times before asking again. Increase the amount of cantering as slowly as your horse needs. Eventually you'll be able to add canter circles an figure 8's just like at the walk and trot.
I don't know your horse so he may already know how to do alot of this. Even if he does, it doesn't hurt to go back and work on it without including more advanced work.
As for his head. If you want to use a martingale that's your decision. I found that the more I worked with my horse the less likely she was to throw her head up. I also found that not pulling on her mouth also helped a great deal.