I treated the enclosure with PAM for the first time two days ago. I had been cleaning it out every other day, but hadn't managed to give Nim a bath. For that I'd have needed a larger tub, and I don't want to infect the larger tub yet. I have seen him soaking a fair bit though, and he seems to have successfully drowned a number of mites. In any case, I think that's secondary to the PAM, and I don't plan to make him take any baths at this point.
Nim ate again yesterday. He spilled some water in the process, so I replaced his paper towels except for the one under the hide he's occupying. I don't want to disturb him so soon after eating, but when I get the chance I'll replace the paper towel under his hide with a dry, freshly treated one.
I informed the seller about the mites last week. He acted surprised, but I'm skeptical. It seems more likely this is an ongoing issue for him that he thought had been taken care of.
Once the mites seem to be gone (hopefully in 2-3 weeks of treatment) I'll PAM the larger tub and transfer Nim over. It's not too large to continue treating with PAM, and it would allow me to avoid issues like the whole floor becoming wet from one spill of the water dish. I cleaned the lid of the enclosure this morning. There were several mites, some of which were still alive.