for TL;DW
1. Disassemble boots, liners, socks and WRING* them all out thoroughly.
2. Put foot gear over heat source (risky if gets to hot).
3. Bring anti-fungal for or to prevent athlete's foot et aliis infections.
4. Keep boots IN-side tent, and do not let them freeze under any circumstances*
5. Put (damp) socks, footbeds, liners, inside jacket and under arms in the tent, even the whole boot if need be.
6. Bring votive candles (tea light pucks in metal tin) and prop inverted boot throat 10 inches over candle, one per boot, and constantly monitor.
7. Shove a nalgene bottle of boiling water (dry threads, check for leaks first) in boot.
* It takes 80 calories to convert a gram of 32F ice to 32F water, and 540 water to steam. Easier to wring out water than boil it off. Easier to keep from freezing than thawing -- if it's wet it's not below 32F, but once solid it can drop further.
I like the votive idea. My SHTF back up has been four grocery bags dry bagging fresh, dry, thick socks. If I submerge a boot, de-wet as best I can, then foot->bag->sock->bag to keep foot from (s)wetting out sock insulation from inside and boot from wetting out sock from outside. Then U-turn back to trail head (summit will be there for another day) and KEEP MOVING to prevent it from freezing solid. If hike is longer, swap at least one pair of bags with oven bags.
I haven't had any submersions in winter yet (knock on wood), but have had them in above 32F weather (other seasons) and from putting crampons on jungle/desert boots to go up a shaded gully in shoulder seasons which wetted out from melt -- they're basically shells with closed cell insoles, so I just took them apart to air out while I switched wool socks (double safety pinned wets on back of pack to dry), re-booted, and hiked them dry.
