Just to add, I had to make a few tries before I found the perfect bitless bridle for my horse. He didn't like the popular Dr.Cook's, because of the head-hugging pressure it has. He didn't respond well to a simple sidepull - it seemed that he doesn't enjoy the pressure points it uses, as he always became very stiff in his neck and poll as soon as it was put on, and we could have used it only for light hacking on a loose rein, no schooling. He goes rather well in a rope halter, but, when I tried the LG bridle and the little S hack, I instantly felt the difference, shown to me by a relaxed, happy and engaged horse. :)
I have come a long way, to surrender my shadow to the shadow of my horse.