I know if I am ever called upon to break up a dog fight, which requires getting the dog to "release the bite", I will grab the tail first which, which will get their attention because they will check to see if it is another attacker joining in the fight - if they do not release the bite with the tail grab, I will go for the ear twist, this almost always will get a release from the bite/hold - if that does not work the only 100% tried and true way to get a dog to let go of the bite and separate the combatants is.... a thumb up the butt *LOL* and having a long tail to hold the butt still, does facilitate this
*LOL* I know more information than you ever needed to know!