One of my ferrets has good ol' rat tail. Red waxy buildup, blackheads, hair loss only goes about halfway up the tail, no hair loss on the body ever so not adrenal. I wash her tail about once a week just to remove the dirt, but is there anything I can do to encourage hair regrowth?

How old?  I think every ferret we've had with rat tail eventually had adrenal.  Eddie had rat tail for a year, then it grew back nice and full, and about 8 months later started showing other signs of adrenal.  I'm not saying it's guaranteed, but it would appear that hormones have some role in it.  Just my opinion.  One thing I used that seemed to finally help clean up the tail was a Noxema type skin cleanser.  I finally tried it regularly after some months, and may have helped grow it back, but it was for naught.  It did help clear up the black heads.

THE DOOKS OF HAZARD