I have had mites this year for the first time. Fortunately I don't have so many snakes as I used to and it has been less of a job to deal with.
After trying the chemical treatment repeatedly and not eliminating them entirely (getting rid of 90% is easy , getting rid of 100% incredibly more difficult) we have gone for a very natural method.
We have put a water bowl into each enclosure deep enough for the snakes to fully submerge themselves. This way the snakes can just drown the mites. During this process change the water every day. It is important to get the right size of bowl. To little water the snake cannot fully submerge. Too much and the snake displaces it making the enclosure and substrate wet, which can be another problem.
You can also physically examine the snakes and squash the offending mites.
And a final slightly more extreme method, get a cloth made damp with a harmless oil, such as olive oil and allow the snake to pass itself through the cloth. Mid you do not choke it - start from the neck down.
I am convinced this is healthier than using chemicals in your snakes enclosure. I know many people who have used chemicals and in the past i have too but i know for sure that water, physically picking them off and olive oil are safe.
Now I am going to run and hide behind the sofa and put on my flame proofs.