If she is white with pink skin, then use quickcolor shampoo rather than quicksilver shampoo. Quicksilver shampoo works better on white hair with grey/black skin, and quickcolor shampoo works better on white hair with pink skin.
Also, miracle groom is the best poo stain remover I have ever used! That is good for removing manure stains in the winter when it is too cold to bathe.
I would also do a lot of currying, as it really helps lift up the dirt from her skin, making her actually clean, not just "looking" clean :)
Hope this helps!