I have routinely done week hikes with sufficient creek crossings that we didn't even try to keep dry feet. (Coral Creek has 22 crossings in 3 miles. Most of the trails in the area have at least a knee deep crossing every hour.)
These trips would be the first intro to the school I worked at. A 7 day trip would cover from 80 to 120 km and 15 to 30 thousand feet of elevation change. Trails ranged from horse trail, seismic cutlines, to bushwhack.
Everyone wears a thin pair of poly propylene socks under a pair of wool socks.
The first day we stop after 1.5 hours walk, and everyone removes shoes and socks for a foot inspection. Hot spots are taped. Kids are taught what to look for. Adjustments are made in how they tie shoes.
Repeat again at lunch and mid afternoon.
Second day we only do it at noon.
Third day we remind people to check their feet at noon.
At the top of a pass we remind people to pull their feet back in their shoes, and tighten up the forefoot lacing. At the bottom we remind them to loosen up again.
Everyone brings two pairs of footwear.
In general we don't recommend boots, but rather high top runners unless the student has a rep for rolling ankles.
In evening after set up chores are done, everyone changes into dry socks and their second pair of shoes.
Some students and staff have tried sandals. Lot of problem with grit. I have tried high top water booties. This works well if you have tough arches. Crocs or sandles are ok for camp shoes.
When we know that feet are going to be wet all day, a slather of vaseline before socks in the morning slows down the foot wrinkling and cracking.
With this protocol we usually got through a week long trip with 20 people with under a half dozen actual blisters.
Toughening feet. These are things that can be done ahead of time.
A: Wear dirty socks. Crusty salty socks essentially soak your feet in brine, which toughens skin. If this is repugnant to you, dip socks in a 10% brine solution the night, and let dry. They won't stink.
B: Rub your feet with 99% isopropyl alcohol. This will also toughen your hands. The alcohol causes the proteins in your skin to cross link.
C: Wear the footwear including socks that you will be using for the trip for a week to a month ahead of time. This gets your feet used to where the pressure points are.
D: Walk barefoot both to callous your feet, and get your mind used to ignoring small levels of discomfort.