Oil and sulfur is the only thing I've found that works. That's basically what Happy Jack Scarptic mange medicine is. I'd rather use NuStock in the tube, it's basically the same too but easier to apply. I wear throw away gloves and rub it in.
I have had dogs with that condition off and on for 50 years, it's hereditary, won't spread to other dogs but you won't ever get rid of it on a dog that's got it. You can clear it up but it will keep coming back for the rest of its life. I have a 15 month dog that it has just showed up on its hind leg (his dam's dam had it). I'm trying to decide if I want to deal with it for the rest of his life or get rid of him now.

I have one that barvecto pill had started putting the hair back on. You have to get it from the vet it last 3 months and cost 50 dollars.