For a halt ask with seat first, so seat deep in the saddle and slow your movement with your horse, say whoa and then pull back on reins, don't yank, your hands should move like 5cm.
Bridle less would take time, do groundwork with your horse, teach it to move away from pressure and then relate that back to when your riding.
It will take time
^This. Real bridleless riding is simply a by-product of good "regular" training. IMVHO, setting out to the arena with the specific goal of teaching the horse to ride without a bridle is training for the result - there will be gaps in training and it will be a lot more work to do that than to simply build a solid "normal" training program on top of a firm foundation.
Start with seeing how little it takes to stop your horse from a walk. Use the progression RedTree outlined - sit deep and exhale, close your legs around the horse, and close your hands. Really think of it as closing your hands, not pulling the reins; pulling is going to distress the horse to some measure, and the horse will resist. When the horse is really really light halting from the walk, and you almost never have to go to the reins to complete the stop, move on to the trot, then canter, etc.
For turning, be sure that you are correctly supporting your horse through the turn with your seat, core, and legs - not just pulling the left rein to go left. Ultimately, the reins should not be there for control, but for refinement. Stephnello is right on the money about the safety aspect of it - don't go straight from riding with a bridle without needing to go to the reins for every transition to dropping the bridle all at once. When you and your horse are ready, start out by just knotting the reins so they stay handy on the horse's neck and see if you still have that control without touching them. They're still there if you discover that you aren't "there" yet. ;)
All of this is part of training any horse who is expected to be light and responsive to the aids, and is doubly important if your ultimate plan is to go bridleless. Just transitioning to a bitless setup probably won't do much for you - it isn't about the gear (or lack of it), it's about the rider.