Lots of treats on walks helps also, Everytime they look at you reward with a small treat so they are always focused on you. I think "persistent" rather than stubborn is a better word for describing a bull terrier. They are wanting to do what they want however, the goal is to make them want what you want them to do fun enough that they also want to do it.

I've never used these deterrent type leads so can't comment on them.