My mare had really bad mud rash a couple of years ago. Managed to avoid it last year, but this year she has got some again on one hind leg.
Thought I had got rid of it last week - had been applying H10 and then one night I chucked a load of water at her leg, rubbed it dry with a strip of a towel and hey presto - smooth clean leg. I brush the mud off every morning normally when it is dry.
Went away for a couple of days and the person looking after did not brush her legs 
and so I returned to hard scabby bits again. My mare is very bolshy sensitive and normally will not let me touch anything that is remotely tender. She is still letting brush at these scabs, but I do not want to pick them as that will only lead to trouble.
Question is, shall I wash leg tonight with hibiscrub and then rub like mad with towel in the hope of removing the scabs? If I do it tonight, for the next three days I can turn her out in her mud boots by which time hopefully the skin will have healed.
It is better to get the scabs off isn't it? She once had to stand in for three weeks on veterinary advice but to no avail - she ended up having to be sedated and the scabs removed.