What I do for my horse smokey is I clip his white markings about 7-5 days before the show with a #10 blade, going against the grain of the hair. Then when it comes time for the show you can't see the lines and/or little mistakes. When I bathe him I first lather him up with a basic dirt removing shampoo I like to use Show Clean i think its made by Absorbine, the same company that makes "Show Sheen", it lathers really nice and smells like apples and it really helps in getting dirt off. Then for the white markingings I use Quick Sliver. I usually let that set on the white for about 2-4 minutes depending on if there are really deep stains. But you don't want to let this set for too long, it might dye your horses white markings purple! I've seen it happen! Then once I'm done bathing my horse and his legs are mostly dry, but still a wee bit damp thats when I brush cornstarch or baby power on to his legs, making sure not to leave any pink showing through. The dampness of his legs will make a kind of paste with the cornstarch or baby power. I make sure to really work it in the hair to it sticks in there and doesn't poof off. Then once I'm satisified I brush off any excess. To sort of set the white on I wrap his legs with polo wraps making sure to cover all the white. Then I remove the wraps right before I enter the show ring.