Through another horse forum, I found out about GOOP - the white gel hand cleaner. It works pretty good, as we have used it on our mini creamello mare, and within two applications her tail was already whiter than we had washed five times with quic silver. The stuff is fairly inexpensive and you can find it at Wal Mart next to the automoblie oil. I am happy with it, as mentioned before, it got our mare's tail whiter than when we washed it. Her tail never got completely white, and as most know, white horses always pee on their tails and turn them a nasty shade of orange. So far, her tail has lightened up, and has stayed white (at least a month and a half after use).
Anyways, here is the original thread from the other forum that has more info on it:
http://www.horsegroomingsupplies.com/ho ... 12671.htmlAmanda