Grab the dog by the hind legs and walk backwards.
Do you have personal experience with that, or is it a guesstimate?
I suspect that if the dog has a hold on a victim, pulling him like that might risk tearing larger wounds. Though it might cause the dog to let go of the victim, you might be its next victim.
Making the dog dead is the best bet, IMO.
Warning: Nobody follow that advise with a pit bull. That is extremely dangerous. You must act as if you intend to kill the pit bull and make sure you have a weapon sufficient to do the job.
Don't stop until the pit bull stops moving but be ready to strike hard again if it shows any signs of movement.
Oh, well I guess that works just fine if you have long elegant legs.