I am a massive fan of Pig Oil for the winter. I liberally coat my horses legs in it every couple of days using a sponge and their legs are usually half as filthy as they would be without anything at all.
I also put it in the bottom of my horses tail again for the same reason. When it does come to needing to wash off, the pig oil makes life easier without the endless need to scrub.
I hate winter and I hate mud, but Pig Oil helps in keeping my sanity.
BUT….. Make sure you allergy test. None of mine have ever had a reaction but I have heard of some horses that have, so better to be safe than sorry.
Equimins does an excellent version called Mud Slide which includes sulphur which acts as an antibacterial agent.