Welcome to happy tail syndrome... My dog gets this every season. (Or did)
I have tried many different approaches to reduce the abrasion, tail guards, vet wrap, mole skin... All worked for a little while but he was always throwing them off.
Finally one day out of a little frustration I wrapped a piece of duct tape around the end, we have not had a bloody tail in two seasons. It does not seem to bother him and after a day of hunting pretty easy to remove without discomfort if you take your time.
My wife is happy now too because we no longer have tail blood on all of the wood trim in the house from when he gets excited and reopened the cut.
Hope this helps!