we've had very good luck with a product called nu-stock. cures red mange, heals hot spots, ring worm, ear mites, etc.
on the web at nustock.com
or call 1 877 5nustock
i bought 2 jars on ebay and will continue to keep it on hand. it's good stuff. really works and smells absolutely awful!!!!! :)
Flowers of Sulfur, or Sulfur Sublimed Powder manufactured by Humco, available at pharmacies, less than $3. I once used this on a stray dog with obvious mange, and cured him. It WORKS! Also, my mom has used the Nustock for hotspots, and says it works. We found it at a feed store.
The whole problem with Demodex is the dog has a poor immune system. All dogs carry the mites, but dogs with a good immune system keep them to a minimum and under control. When a dogs immune system suffers, the mites can take over and become a problem. Dips and chemicals may work to kill the mites BUT the also kill the immune system (the actual problem!) even more! So they will make "what you see" go away, the symptoms, but only make the REAL problem worse.
We had a dog here with demodex once... we put her on a good all natural raw diet, gave her vit C and other immune boosting herbs, and it easily cleard up on her own! I would not use the dips/chemicals for this. I also would not give any chemicals on the dog - meaning no frontline or other flea preventative like that, no vaccinations, etc...
There is info out there on the net about treating it naturally if you look it up on a search.
May I suggest fresh lemon juice applied with a cotton swab? It dries the areas and provides certain nutrients that the skin needs during this time.