We start them all wearing a bit but with the long reins attached to each side ring of the noseband of a headcollar (worn over the bridle), on a circle. So in effect you're lunging with 2 reins, one on the inside rein and one going round their bottoms (where a fillet string would go). When they are comfortable with the rein round their rear ends, we turn them away from us so they are going on the other rein. It takes a bit of practice and you're likely to get in a tangle the first few times so be sure your reins are properly coiled and you don't get your hands stuck! In an emergency you can drop one rein and hold onto the other without risk of the horse standing on the dropped rein and injuring his mouth as he might if the reins were on the bit. Once both you and the horse are proficient at turning away and going on the opposite rein without ending up like a ball of knitting, it's safe to put the reins onto the bit rings. With practice, you can long rein a horse in trot in figures of 8. Once the horse is working well to the voice, and understands what he's doing, we then start driving from the bit and also by walking behind them. We start hundreds of horses of all shapes and sizes this way. By getting the horse accustomed to the reins before going onto the bit, it avoids pulling delicate mouths around. It also avoids the horse taking hold and running away with you behind him! (Been there done that!)
There's lots of ways of doing the job, this is just one that we use and it works for us. We get lots of comments about what lovely mouths our horses have too!
Kate