Krud kutter by QT horse shampoo
Curry and brush before bathing, then use a curry to scrub the soap in
Yes curry mits are great to really get the under dirt and grime from the coat.
I found a great scrub brush that's a little like those dish scrubbers you fill with soap. You fill the handle with shampoo and the head has a sponge in the middle with bristles around it. Works AMAZING for scrubbing dirty horses anywhere. Leaves them really soft and shiny too
try using a curry mit white applying soap and when washing out.