Well, it has been a while since I did the poor man's flamethrower with a can. In that case, switch to Justice Brothers Green Label Carb Cleaner. Even if you don't get it ignited, the chemicals alone might be enough to fully inebriate the beast. We used to go after hornet's nests with a can or two; the hornets would pop out of their nest, we'd zotz them and they'd be curled up and dead before they hit the ground, not even a twitch left in them. Better'n any wasp spray I ever used.

One more thing, a guard dog behind a fence can almost always be baited off of an attack. It might take a 5 lb chunk of meat, but once they get their mouths on it, especially if someone keeps a hold of the other end, they likely will refuse to let go, allowing the trespassers to come and go. Fresh pigskin fatback is preferable, as it won't rip apart easily, and is nigh irresistable. Once they start doing the tug of war with you, they become nearly oblivious to anything else. It takes a really well trained dog to overcome such a distraction.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)