Thank you, that's a very good point. I actually did pre-treat several sets of paper towels with PAM and left those at the family house with BP #2, so they would already have those prepped in case substrate needed to be changed for pee/poop clean-up before I am back this coming weekend. If the pre-treated towels are still good for up to 2 weeks out, then I'll prep a larger supply of them both there and at my apartment. For ventilated areas, the family home has an outdoor patio area, and my apartment, though on the 4th floor, has a serviceable little balcony I've been using for this purpose.
Thank you for the well-wishing, and best of luck to you as well. That's really unfortunate about the cork bark - with such porous and uneven material and with mite eggs being so tiny, there's probably no way you could have detected that until the mites already started hatching. As you say, I may also go with continuing to PAM-treat at least the paper towel substrate for 2 full months rather than 1, for both snakes, just to really err on the safe side.