Slowing horse down

Question
I recently moved to an area of the country that engages primarily in western riding and activities such as pleasure, cutting, gaming, etc.  There are shows every weekend, penning competitions and plenty of activities that are horse related unless you are an English rider.  My horse is a x-country hunter/jumper with a lot of go and nervous energy.  I would like to "fit in" with the locals, but my horse has no "turn" for barrel racing, no cow sense for cutting/penning, so I thought maybe he could learn to be a western pleasure guy.  However, everything my horse does is fast.  He walks fast, trots fast, goes fast.  When I work with him and he starts picking up speed, I ask him to stop, then we begin again.  A month later we are still doing the same thing with little improvement at all.  My horse can walk faster than the western pleasure horses canter (sorry, lope).  He's always worn an eggbutt snaffle.  I've been trying a Tom Thumb bit so I have the required shanks, but still the broken mouth piece, but he is so sensitive to this bit that you can barely pick up the reins.  So I guess I'm saying, I can bump him back slower, but then need to release totally and he just picks the pace back up again.  The horse knows what I want because when he starts picking up the pace, he will stop himself, start again slower and again pick up the pace.

Answer
Hi Sky,
I mainly train for western (trail riding) type of riding. But I have great respect for the English riders. English improves good balance and good posture. I'm sure somewhere around there are folks who ride English. Slowing a horse down has nothing to do with your hands. In fact, your hands are the most aggressive tools you have. I do not use my hands all that much. I use my seat, body and legs to work a horse. My hands are the very last thing I use.
The Tom Thumb bit can be a very harsh bit for a horse in the wrong hands. It takes very light hands to use one. It has what I refer to as a "nut-cracker" effect in the mouth. As you pull back, the shanks pull the bars upward at the broken point much like a nut-cracker and can cause pain in the mouth. I have several of these bits..and I do use them...but not until the horse is well schooled in other bits and responds to my seat and legs. And when I do use it, I'm very gentle with it.
To get a horse to slow down, I don't pull on the horse. Try putting your horse on the rail in a snaffle. Give him a loose rein. This will be a one-rein exercise. Only use one rein at a time. Only use the inside rein (the rein towards the inside of the arena). Ask your horse to trot. If he should speed up, gently BUMP his nose toward the rail with the outside rein. Not enough to turn him, but to bump his nose towards the rail. This should slow him down. At the same time, sit back on your pockets. This will take tons of repetition. It won't happen overnight. So please be patient with him.
Some horses are bred for some things and not for others. Your horse may never be a "western pleasure" horse. Please be aware of that.
Good luck and above all...remember why you started riding and got a horse to begin with. To have fun.