Hum... I don't think it is something easy and unsignificant to train a horse to ride it bitless or bridle-less... I wanted to do that, because my horse has always had a small problem with bites - he never feels at ease or comfortable with them. So what I did was to do all the work as if he was a foal... Lots of hours on foot, teaching him how to respond to my voice, posture, gestures, to give in to the halter, to a rope that comes against his head, neck, legs, hips and so on, in fact I tried to teach him that when I seem to ask something, he must rely on me, follow the sensations of my body or of objects on his body, and think, not flee. Tried to make a "reasonable" horse that takes part in education in a word.
Then, once he was perfectly cooperative on foot and knew the words and responded to a mere halter without questioning me, I began to mount and dismount, just training him to stay quiet while I mount, dismount, without having to hold him. I wanted him to be responsible and self-sufficient, he knows the rules, I want him to follow them by himself, on the basis of a kind of contract: you do things right, it's comfortable, I'm happy with you, there are treats, massages, strokes etc, you do not do things as you are expected to, I intervene to put you back onto the right path, without losing my nerves but I say "no" and act.
Once I could mount/dismount easily, I asked him to give his head while I was on his back, still. To the right, to the left, same ideas: think, follow me, be calm, relaxed. Then I saw I could have his hinder legs moving sideways, which combined to the head can help stop him if he really does not answer the "aaaoooo stop". As for his front legs I still can't really get them to move independentally on foot so I do not try on his back. Then I began to walk with the known orders, "au pas", "tourne" etc, using first my voice, then my seat/back/shoulders (the softest aids after the voice I think) then my legs, then the reins on the halter.
For a few months we only walked because I felt unsure if we would be safe trotting. Then once I could turn and stop easily we began to trot, and so on.
What I mean is, it is not an easy or quick thing! It is like "breaking in" a horse. Moreover, I don't think it quite good to intend to use your legs only: there are so many things to ask from a horse, do you really think that only the place your legs are acting or the way they move/press, will be enough for all the orders to give? You'll need to use your seat, the way you put your shoulders, your pelvis, where your eyes look... many, many things (even the wa