umm... I do not agree with having the horse go backwards. What you want to be is like an electric fence. Have you ever seen a horse touch an electric fence after they know what it does? No. You want to set up 2 zones, a blue zone and a red zone. Say ur the red zone and you horse is the blue zone, you don't go into there space and don't let them come into theres. When you horse starts to swing his head around have your hand already up and if he comes into your space block him with you hand and lightly pop him on the nose or check. In reality you don't hit your horse is the face, never do that, but the horse is running into your hand, he is the one that made the decision. This will not make your horse head shy as you are not attacking him. I have tried doing the whole backing your horse up and then it can get bad... DO NOT TRY IT! I have had my horse become worse with that and you also don't respect his space. My horse has gotten so irritated with me she has reared. With the zones she stays in her space and I stay in mine and its all good, we both respect each other. With backing up they get scared. When you think about it when a horse came into the lead stallions area the stallion would just bit/kick the horse but they never chase them away, horses don't need long drawn out punishment but quick and too the point.
Bandera 6 yo Hano x Canadian Crescent Star Eventing Team