As an experiment, tried not only the iodine, but scrubbing with a toothbrush on one my most docile cows a few years ago (with cubes to keep her occupied and not hating me quite as much). Did it daily for a week. She didn't seem to heal any faster than the others. I've also been told that anti-fungal cream (like for athletes foot) will help the healing process. Maybe it will, but I have better things to do than worry about something that will clear up anyway.And you can speed it along with gracious application(s) of iodine.
You left out apple cider vinegar, the cat daddy cure-all of the whole livestock civilization.Ringworm takes about 6 weeks to go away on its own and about a month and a half if you treat it with stuff like bacon grease, Fluid Film, iodine, motor oil, vagisil, athletes foot cream, and every other concoction.