I have worked with quite a few off the track T-breds--Gulliver and Henry came straight from the track to me as did others that I worked for other people--and I always spent about 3 months hacking them. When we started the ring work, the focus was on inviting them to stretch to the bit while establishing a slow, but steady tempo that would help them find their balance. They should not be expected to go "on the bit" for several months until they have found their balance. Once they come into balance, they will stretch their top lines on their own and will come quite naturally to the bit. Having a good sense of tempo is essential if the rider is going to be successful in getting the horse into balance and initial self-carriage. As Kimberly Clark pointed out to me, race horses learn to function using momentum. Dressage requires an entirely new sort of balance. The horses--if one is to be fair--must be given the chance to change their way of going over time. Forcing them to become something that their bodies have never experienced is totally unfair to them.
On the topic of cues and aids: I always think of a cue as something a horse has to be taught and an aid as something that is a natural response. I don't think a horse should be asked to figure out what is being asked of him. I think it is very difficult for a horse to function this way and in the process of having to "figure things out" they become worried, and usually very tense. These are the horses that anticipate movements especially in a test. They worry enough about doing what they are supposed to do that they anticipate what they are supposed to do in the hopes that what they have figured out is ok. Anticipation is to be discouraged whenever it occurs. It is up to the rider to put the horse into the mental framework to be able to relax and simply allow his body to respond to the aids. Most of the aids should promote a natural response.
For instance if the rider has made the effort to cause the horse to step forward to the leg (the leg should never tell the horse to step sideways), then the piaffe will be a natural culmination of this "forward" inclination. If the rider has caused the horse to bring the left hind forward to the leg and to the left seatbone, the canter depart should be a natural culmination. Then when the same has been achieved to the right, a flying change is not something that is "taught" but a natural response to the aid to take the right lead. The horse then does the flying change as a canter depart in the other direction.
There are things that must be taught, but they should be thought of as conditioned reflexes: The voice aids when lunging should be taught in such a way as to condition a reflexive action. They should be presented in such a way as to cause the horse to respond without thinking. When the ground person says "walk" there can be no response from the horse other than to walk. He should not have to think about it. These voice aids are used in the early training of the horse under saddle. The horse has no clue about the driving aid when first broke. A kicking leg is confusing; often the horse will turn his head toward the rider's foot and will try to bite it if it is too annoying. However, if the horse has learned to walk with a voice command, the rider can begin to combine the voice command with the action of a driving leg to condition a reflex in the horse to go forward to the leg. The pushing seat to cause the horse to go forward is dependent upon the leg aid. The whip actually is a more natural aid in that the horse is very likely to step when he feels the whip.
Other aids, such as the squeezing leg to bring the back up or the seatbones for the bend (or simply turning in the early stages) or the lifting of the chest in the rider trigger natural responses in the horse. Horses seem to have a natural response to the restrictive action of the outside rein, but sometimes need to be conditioned to this aid. The closing of the knees acts as a restrictive aid on untrained horses but has to be re-established on horses which have been ridden by riders with tight thighs. All in all, what i am saying is that horses should not have to "learn" any thing. They can "learn" not to dive into the bit, but they should not have to "learn" how to carry themselves, how to do leg yield, how to halt, how to do shoulder-in, how to do flying changes, how to piaffe..............all of this should be a natural culmination of the training.
Most of the work I have had to do throughout my life has been to unravel the cobweb of anxiety that has entered the brain of the horse and to put him into a position of understanding that all he has to do is relax and allow his body to respond naturally to my body.