The whole reason that mud fever occurs is becaue of dampness getting to the skin on a regular basis. This can be rain/mud, damp bedding in stalls, even heavy dew on the grass. So the biggest concern for preventing or getting rid of mud fever is to get the horse out of the damp conditions.
The legs should be cleaned with an antibacterial/antifungal shampoo or scrub such as betadine. Then the scabs should be removed. This is easier to do if they have been allowed to get wet and then scraped with a plastic spatula. Once the scabs are removed the legs should be dried THOROUGHLY. (I can't stress that enough.) Once the legs are dried, a layer of desitin or other diaper rash ointment is applied to help prevent moisture from getting to the skin. If the condition is pretty serious, an antibitoic cream (simple triple antibiotic) can be applied. If there is significant inflammation, a mixture of triple antibiotic and steroid cream can be applied and then that covered with the diaper rash ointment.
There is no need for other "miracle cures" to treat these types of conditions. This is a simple bacterial or sometimes mixed bacterial and fungal infection that occurs and continues because the main issue of dampness isn't addressed. The chronic damp conditions break down the skin's basic defense against these infectious organisms that are encountered.