Interesting, today I discussed this very act of self defense with a fellow softball player when we were talking about being attacked by a large dog........
There's another tactic involving large dogs but I wouldn't advise it against bears...........LOL!
Wotked with attack dog trainer wearing body pad protection. Always had great fear while off-duty, a Doberman or German Shepard would attack me unawares. Decided the only defense was a strong defense. Here is the technique I practiced but never employed:
Dogs always bite what you offer, raise offered leading arm and prep the back arm like a straight sword, flat hand pointed tight fingers. The dog will always leap at the target, mouth wide. Then, like a matador, thrust the sword-like hand down the dogs throat.
This knowledge gave me confidence I could easily kill a dog. Thankfully as yet, this remains a theory.