I only use Provent-a-Mite on incoming snakes for QT* and all QT snakes are kept on paper towels. I spray the enclosure 24 hrs in advance to give more than sufficient time for it to air out before adding the towels, water bowl, hide and snake).
I would not suggest using PAM on a porous substrate like bark or coco husk.
(*learned my lesson in the 90s when I brought in a new snake in that had mites and didn't QT, had to treat my entire collection, only 5 at that time, moved everyone to paper towels until they were eradicated)