My horses HATED the doctor cooks bitless. I think it had something to do with the presure being distributed to so many different points, even though I have very soft hands. Tried it on three horses and gave up. I use a leather side pull that a local guy made for me. I'll have to get a picture, it looks awesome, is simple and works great. I'm not a big fan of mechanical hackamores. I also regularly ride in a rope halter.
I figure if a horse can feel a fly landing on its bum, it can certainly feel me pulling on a halter and respond accordingly