As always, some good advice showed up in the comments to Harvest post.
Andrey suggests using 9 frames not only in the honey supers, but also in the brood chambers. Interestingly, he says “let bees draw out foundation first then remove one frame.” I’m curious, though: why let them draw out ten frames and then remove one, rather than just start with nine?
On the mite front, Andrey pointed me towards Thymol as a natural remedy, in addition to affirming the need for a screened bottom board. I did a bit of reading on Thymol, a derivative of thyme, and it does seem safe (although I’ll admit I’m often skeptical of the belief that anything “natural” or “plant-derived” is somehow intrinsically safe). An article from BBC News suggests that it can kill off 90% of the mite population. Might be worth a go.
Finally, Beek pointed me towards a “clearer board” or “Porter”, a device for getting the bees out of supers without wasting hours trying to brush them off. Best I can tell, it’s a sort of one-way door you put into your hive, so that they can exit the supers but not re-enter. Leave it in for 24 hours and all the bees inside will have dropped off honey and headed out to gather more, then not been able to get back into those boxes. The nurses and such that don’t leave the hive will be down with the brood, so you should have relatively bee-free honey supers you can just pluck off.
Great. NOW you tell me.