A poor man's mite treatment is 5% seven dust. I have only had to use it once. I took the snakes out and dusted. I then waited a couple hours and vaccumed up all the dust (and substrate). There will be a little residue that will keep killing the mites for months to come. If your snake has a bad case, soak them in the tub for immediate relief until you can treat the enclosure.
I'm so far Right, it's amazing I haven't fallen OVER!