Shona, there is an old joke about a man who goes to the doctor and says "Doctor, my arm hurts when I do this (he raises his arm)". The doctor says "Well, don't do that".
If your horse bucks or acts up with spurs - don't use spurs. I've used spurs all my life but my current horse HATES them and will act up terribly if I touch him with a spur - so I don't use them!
Here is a website to training a one rein stop: Training ~ One-Rein Stop Hope that helps.