I treated a dog successfully for mange with applications of green clay, and a couple common essential oils. I believe it was Cedar, Pennyroyal, and Tea Tree. Neem couldn't hurt either.
You have to cover the clay pack with a bandage, or cover with a another layer of cayenne/mustard to keep the dog from licking or scratching.
This dog was bad off. Completely mange free in three weeks-with obvious hair regrowth.
At the same time I made sure that the dog was eating healthy by using food with no animal by-product meal, beaf, chicken, corn, soy, or wheat. Also start giving the dog RAW bones.