I don't know if this would work, but I had a mare who would throw her head up and back away fast when I was trying to bit her up. I put her with something behind her and against her right side, and turned her nose towards me to bit her up, with my arm over her neck. I had to do this for about a week, and she would accept the bit very nicely after that once she respected that she couldn't get away. I don't have anyone to help with things like that, so pretty much figure out a way to get things done. Good luck with your horse!