Many years ago, more than I care to remember, I worked for the Ontario Humane society. We had a dog with mange come into the shelter. It was a little female beagle that soemoen had found.
I had our vet check the dog and he gave me some shampoo to try. I don't know what it was, but it looked like mustard.
I followed the intructions, kept the dog isolated and she came from no hair from her ears back to fully recovered.
It took some time, but we began to see improvement farily quickly, so it encouraged us to keep going.
The dog went on to many years of hunting rabbits with me. Pound for pound, one of the toughest dogs I ever had.
Sorry I have no idea what the stuff was.