There are several good articles on TheHorse.com for skin conditions. You need a free registration to read the articles. The Horse | Rain Rot
Bleach is not very good for skin. It can change the pH and decrease healing. Iodine is a good anti-microbial. I have had good success with Equyss MicroTek shampoo, when used as directed - let it stay on the horse for 10 minutes or more before rinsing. My vet recommends it as well. Be sure to soak all grooming equipment, towels, and saddle pads in anti-microbial detergent. Equyss makes a blanket wash.
Skin infections can signal a compromised immune system. Take a hard look at their diet, and supplements to make sure they are getting adequate vitamins A, C, D, E, and selenium.