I found the very perfect way to defeat the third bowser in Mario 64. When you meet the third bowser, try to make him run toward you by running around in front of him. When he begin to dash toward you, run toward the bomb. When you and the bowser are very near the bomb, do the flip-back jump. The bowser will have a hard time trying to balance himself. During that time, go behind him as quick as possible, and pick him up. You will be able to throw him at the bomb easily. But if you do not throw the bowser near the bomb enough, he still need some time to get up. During that time, go pick him up and throw him to the bomb again.