Rain Rot Help???

I've had my horse for about 3 years but this winter has been very rainy and muddy and he got rain rot. I was wanting to know how to treat it. I know that you are supposed to wash them with anti-fungal and anti-bacterial soap but its way to cold (20 degrees). I have heard many different theories such as vitamin A supplements, Listerine, cortisone cream, MTG, iodine shampoo, betadine, human ointments, apple cider vinegar, athlete's foot spray and ointment, bleach, and toothpaste. I just wanted to know what works right. I would like something cheap because I don't really have that much money. It is a very mild case on his back and hindquarters, I just wanted to treat it so it doesn't get worse. I tried riding him but the blankets hurting his back. I have all the basic home stuff like toothpaste, bleach, anti-fungal and anti-bacterial soap, Listerine, cortisone cream, athlete's foot stuff. Just wondering what I should use.

Dumor gold supplement and a decent name brand feed. All the topical solutins in the world wont keep it from coming back if you don't treat the main cause. Namely vitamin A and probably other nutrition deficiency.
Ever notice skinny horses always seem to be most likely to have it bad in the winter ?