I'm having a tough time teaching my QH to walk at a good clip. She likes to mosey and I like a good fast walk. Not meaning to hijack the thread, but I figure the OP might get something from this as well.
I saw something on the Internet from a trainer (can't recall her name), but she is pretty well-known. She takes a piece of stiff rope, like a piece of an old worn-out lariat, and makes a loop around the horse's rump, such that it hangs down to just about half-way down the gaskins. She ties a knot in the middle of it and attaches the ends to the rear cinch rings. As the horse walks, the knot hits the horse's gaskins, causing it to short-stride and step quicker. She has some goofy name like "hope rope" or something like that for it. I think I may give it a try. I am open to other suggestions, if anybody has any.