Have you ever trained your dog to sit? What did you say to your dog after you told it to sit? You probably told it to "stay." Why did you do that? If the dog sits, he has to stay. In the same respect, I don't have a "stop" on my horse. I only have a "go" and a "back."
Now, I may only want the horse to stop - but in his mind he should be thinking "back up." If I were to ride forward and then stop - and then apply more pressure to the rein to back up, then I'm teaching three cues there. One "go," two "stop," three "back up." So in effect what I'd be doing is telling the horse "Four pounds of pressure on the rein means stop, six pounds means back up."
So, if I really want to make my stops quicker, I only teach "go" and "back up." Now, for you reiners, I'm not talking about how to lengthen the slide here - I'm talking about getting a quicker, more responsive stop. I'm teaching the horse that when I say stop that means stop.
My goal is to take away any hesitation time, with no pause between moving forward then moving backward. I work on "go" then "back up," "go," then "back up." Tip: Only work on this for about 10 or 15 minutes at a time. If you work too much on this the horse gets tired and it gets to be too much.
What you do is to simply ride forward then ask the horse to back up - each time with less and less hesitation. Now, it's not going to be pretty - but you've got to do whatever it takes to "go then back up, go then back up." Your goal is zero hesitation. Pretty soon, as soon as you touch that rein that horse just shoots back.
If I do this with my horse, for about three minutes, I can make his feet "pedal" underneath him as he tries to go from forward to backward immediately. He was moving forward but then, when I ask for the back up, he'll keep his hind feet moving underneath himself. As you're practicing this exercise remember: If you continue to allow the horse to hesitate (instead of whittling the hesitation down to zero) then you won't be making an improvement