Just as an FYI - he didn't get mites randomly, and he didn't get them from your dog. He either had them when you got him, or you carried them in on your clothes when you handled a snake belonging to a friend, or at a pet store or reptile show. Or a friend carried them in on their clothes and then handled your snake.
What did you spray him down with? Be prepared that he could get mites again, as the eggs generally hatch in about 30 days. Provent-A-Mite is what is recommended to eradicate them.