Lots of it, unfortunately :-). Tomato juice and vinegar works as well as anything...
OTOH, we had a Catahoula that made great sport of them, and never once got "hit" -- he'd learned (before we got him) to come in from the side, hit the tail with the right front paw, and crunch the ribs with the first chomp. I saw him do it twice. He wasn't a house pet -- best danged cow dog I ever saw.