The comb and around the eyes... you have to be careful using anything, not to get it in the eyes or nostrils or mouth... but, I think that since Foul Pox is not curable, and simply has to run its course: the only thing you are trying to do is prevent infection, so any "animal" antiseptic would probably work, even "Neosporin"? Ask the feed store owner/manager, they usually know what people buy to prevent infection, or what is safe to put on and around the comb and eye area. Use fingers or q-tips, have someone hold them and be careful not to get anything in their eyes, also see if it will "melt" (Neosporin will) and drip down into the eyes after applying. Use little.
Someone else might know if an oral antibiotic would be in order now or later, as the Foul Pox progresses through the flock?
(Also, check for mites... look carefully at the eyes, rub the area that is blackened on the comb and see if it rubs into your fingers, like dried blood. Look under the wings, on and around the vent area for mites or lice. Treat mites or lice with Sevin Dust, IMO, repeat in 10 days... clean and lightly dust coop, dirt, nesting boxes, roost, and, of course, chickens, under wings, vent, where tail meets the back, and some say a bit in the upper back/shoulder area as well. Not on the face/head.)
Good luck.
