Wow, if he is reacting that badly to bit pressure, get his teeth and back checked out. That's not normal at all. This should be your first step.
Also, what kind of bit are you using? I noticed in another post you were asking questions about getting him off the forehand for western work. Are you using a shanked bit? If this is the case, you should not have a direct contact with his mouth as you would with a simple snaffle because of the leverage that a shanked bit gives you. Either way, I would also check the bit's fit and see if that is causing him to give these extreme reactions.
The way to get a horse on the bit is to focus on the hind end. The horse must be coming through from behind and pushing with its hindquarters to be able to take an appropriate and consistent contact with the bit. If he is falling on the forehand as you mention in your other post, you will not be able to get him correctly on the bit. His head shaking and general protest (if not from pain) is most likely a result of not having enough power from behind for him to put into the bridle.
Getting a horse off his forehand and onto the bit is a long, complex training process. You first need to obtain a consistent rhythm from the horse, which requires a certain amount of strength on his part. So that is where I would start out. I would ride him with virtually no contact (and any contact used for steering or lateral work should be a vibrating, non-pulling contact so he can't lean on the reins) while focusing on maintaining the same rhythm with my seat and legs around the ring and during figures until he learns to hold himself. Half halt when he speeds up, and push him on when he slows. This small step takes time for the horse. How much time will depend on your consistency. Once you get the rhythm, you can start asking with your leg for more power from behind (without losing the rhythm) to catch in the bridle. The contact in the bridle always comes from the energy in the hind end.
To get him off his forehand, you will need to work on strengthening his hind end to carry his weight. Lateral work, transitions, and ground poles or hill work will help. Don't let him lean on the bridle. Don't worry about him taking a contact with the bit just yet. He needs to learn how to use his body and build strength before he can stretch into the bit without simply leaning on it or yanking the reins out of your hands.
Like I said, this is a complex process in which everything sort of builds upon each other and there are a million different ways to get to the same end result. But there is no real order of operations when training a horse. Each horse is different and while we can say that there is a typical "training scale" in which it seems like there would be a simple step-by-step process for training a horse to self-carriage, it doesn't always work that way in practice. It is almost impossible to properly explain how to get a horse on the bit over the internet without knowing the horse and rider. I would really recommend working with a good trainer to help you feel for these things and to know when you can move on to the "next step."
