My Rowdy bucked like a bronco too!
But then after a few minutes of bucking, he settled down like he didn't even have it on. Then the next time I put it on him, we did the bucking again and some of the mule walking (backing up) when I put on the leash. With patience, he learned. Brian Killcommons (sp?) recommends that you put on the leash, kneel down and call him real happy-like, somewhat like play. When he comes to you with the leash on you reward him and you keep doing that till he learns that it is a fun thing and that walking on the leash will be fun, get him places, and when he bucks, or sits, that is all that happens and he doesn't get anywhere. But when he comes to you, he gets to walk, explore, gets a treat, or affection, etc etc. It takes time and patience, but it works.