Rule of thumb, always treat new additions for mites regardless if they have them or not. It's a good preventative measure.
Soak your mite infested snakes with a drop or two of dish soap.
Take out all enclosure accessories and keep the set up minimal. Paper towel substrate, hide, and water dish.
Everything else should get sanitized in boiling water. Same as the enclosure itself with bleach if you want.
Provent-a-Mite is the best mite treatment. You cannot spray it on the animals themselves, only the enclosure. But it works very well.
Spray down the empty enclosure and wait for it to air dry. I personally dry it out for an hour before putting any animals in.
I do this for all new additions as well as one that I bought with mites. Never saw another mite after the first treatment ever again.