The spots on the combs, or if you get some on the wattles..ignore them completely.
They will stay clean, and heal well, all on their own. The only possible hick-up is if the poultry start picking at each other. So, make sure they aren't crowded, and keep them busy.
As to feet....wide perches, WIDE perches!
Use perches where the perching surface is close to 4 inches.
If the bad stuff has already happened.. (Frostbit feet), that can be OK, or a royal pain, depends on how bad it is. Try to look at them, easiest if one person can catch them, and hold them, so you can look at the feet. Odd black spots might be frostbite. If the frostbite is on the tips of the toes, it is possible that you can do nothing and the dead part will just rot and fall off, no problems (well, I guess that isn't really a 'no problem' thing, it is disgusting, and it is painful for the chickens, the frostbit combs and wattles don't seem to bother the chickens that much...just to compare the two). Big problems are if you get frostbite in the middle of the toe, with healthy tissue on each side. Then you have to worry about infection, actual bandaging, doctoring, and still an iffy outcome.