I've always had good luck with Happy Jack. Put a pair of rubber gloves on, slather the dog down, leave'em in a stock trailer over night to let the stuff set up and them cut'em loose and by the time that stuff wears off the mange is gone.
Its stinky but it works and it doesn't cost but about 13 dollars a bottle.
Oh and I've used it on stray dogs that were covered in mange and didn't have but about 3 hairs left and all of their hair grew back in a couple of weeks.