Hi, mites can be a real pain but with some persistence you should be able to squash them. To start, remove anything from the cage that isn't absolutely necessary (as in you should only have two hides, a thermometer, your heat source, and a newspaper/paper towel bedding). You don't need any more problems than you have, so just remember K.I.S.S. (keep it simple stupid) when going about this. No more than necessary.
Everyday you'll want to wipe down the enclosure with a bleach/water mix and then rinse it out afterwards with pure water. Soak all cage furnishings in this mix, rinse with water, and replace the bedding.
As far as the snake goes, you can use some lukewarm water with a little bit of dawn soap and lather it up real good (being careful to avoid getting the mixture in any orifice). Then, wipe the animal's head down with mineral oil and rinse everything off.
I used to have three water dragons, the third being a subadult male from petsmart that was obviously wildcaught. He was covered in mites, filled with parasites, and pitifully sick. He did, unfortunately, succumb to his conditions, although I used that method to treat him and his cage for mites. Just remember that everyone has a different method when treating mites, and what might work for me might not be the same for someone else.
Btw, I think you might find this link useful:
Getting rid of reptile mites
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