You need to work on desensitizing him to things. You can blindfold, twitch, trick or force him into it but that is not fixing the problem. It will actually make it worse and can lead to a really bad situation. Start with something small, a saddle pad or a towel and work until he’s comfortable with that all over him then move up to something a little bigger and so on until you can try the blanket. Look up Clinton Anderson’s approach and retreat method for a good how to. This is extremely important to do but will take some time. If he has a stall and lots and lots of hay he will be fine for now. He’s better off that way then getting himself or you hurt because he’s spooked by his blanket.