Its merely getting to a level of training in which you don't need a bridle, even if it was on.
I have done some limited bridleless work with Jake. He can walk, trot, turn, stop and back up easily. Anything more than that I doubt I will ever be able to do because of his personality. I've been stuck on his back with him racing around the arena at full speed, a few times while I was experimenting with bridleless, all experiences I never wish to repeat.
After I reconsidered, I started working on cues that needed me to not touch the reins. He is sensitive to my seat and legs already so it was easy to teach turning. I would apply the leg cue, do a very subtle neck rein, and reward for the turn...eventually the rein had less and less movement. Everything was the same pretty much, my whoa is mostly verbal. But I would sit and squeeze my butt cheeks together and say whoa, and he would stop. For Back up, I sit back, squeeze with my knees say 'back' and alternate leg pressure.
For a while I used the rope around the neck technique. It was something different and with less control but gave the general idea. I would have a bridle on and the rope around the neck. The bridle was there in case things got out of hand, but the rope was the main source of cues. I have also found that bridleless is easier bareback, I'm able to send my cues clearer that way.