(snark warning) yeah, I rub food on my body whenever I’m in bear country!
What works for me is to change into dry socks when I know I’m out of the wet for the day. That might be after the last stream crossing, it might once in camp, it might be only when going to bed – it depends on the terrain and weather. I try to keep the wet socks as warm as possible to help them dry overnight and if I know I’m doing lots of stream crossing, I might have two sets of day-time socks in rotation giving each one a day on the outside of my pack to dry out.
As for goo, the only thing I bring is a small tube of anti-fungal cream. There are many over-the-counter options but those tubes tend to be pretty big. I like progressional samples because they are typically stronger stuff and in nice, small tubes. After a couple of days in hot/humid conditions or a week of cold/wet hiking I can get a few spots of athlete’s-foot between my toes. I’ve found that putting a dab of anti-fungal cream there every 2-3 days, for me, prevents the problem from occurring.
I don’t have great data on the following, but I like the theory: if your feet are warmer at night and have more circulation, it will help them heal (poor circulation certainly is very bad for healing). So, “if your feet are cold, put on a hat” while sleeping. If your whole body is a little cold, your body will shut blood away from your lower legs.
When I’ve had a slightly warmer-then-needed sleeping bag, I unzip the bottom (or toss the quilt off my feet a bit) and that definitely helps keep my feet drier at night.
The SciFi author Robert Heinlien’s main protagonist, Lazarus Long, goes back in time and ends up in WWI trench warfare. Knowing he won’t have dry nor sanitary conditions for months, his lover’s father (actually his own grandfather) says, “If possible, have your feet clean and dry. Smear your feet all over and especially between your toes with cold cream. Or Vaseline, carbolated is best. Use lots, a thick layer. Then put on socks-clean if possible, dirty if you must, but don’t skip them-and put your boots on. When you first stand up, it feels as if you’d stepped into a barrel of soft soap. But your feet will thank you for it and you won’t get jungle rot between your toes. Or not as much. Take care of your feet, Ted, and keep your bowels open.”