When I start my horses to bit, the first thing I do.... Is teach them to turn using the halter.
You get a halter that fits like a side pull. There is a couple of ways to do this.
The best way is to have some help.
Clip driving reins to each side of the halter, have another person clip a lead line onto the halter where it would normally go. You can run the reins through a surcingle or not, which ever way feels more comfortable to you.
You have your helper lead your horse, You walk behind your horse holding the reins lightly. When you say "Walk on", your helper walks on, and so does your horse. When you say Left/Come, your helper will turn left, at the same time lightly pull on the left rein. To turn right, say right/Get, doing the same thing. Remember with each turn you will have to make sure the opposite rein is not tight, as you do not want to give mix signals.
Take your time, stay at a walk. As your horse gets more and more used to using the reins to let him know where to go, you will need your helper less and less. Once you no longer need your helper, then he is ready to move onto a bit.
Have simplified this a bit.
Doing it yourself is a little more complicated, but will explain if you are interested.