Forget the PAM. Go straight to whatever local pet shop or supply store sells the 'Reptile Relief' mite spray and use that. So gentle, it's basically harmless to your snakes, you can spray it (conservatively) right on them. You still have the same amount of work ahead of you, gonna take about a month to fully get rid of them. But the Reptile Relief takes the guesswork out of "Did I use to much and poison the snakes?" and is just as effective as PAM. Mites are stressful enough as is.
A whole month to eradicate, wow.
I have never had a problem using lice bedding spray, when treating enclosures. I do not treat my snakes with it, they only get soaks. I usually only have to treat once and the mites are eradicated.
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"The greatness of a nation and its moral progress can be judged by the way its animals are treated." - Gandhi