When showing Shire horses the way we get their feathers white is to rub the lower leg with Pig Oil. I am not sure if you can get this in the US but any vegetable oil should do. Rub this well into the feather making sure it goes right to the skin and leave in for about an hour.
Then wash off with plenty of hot soapy water and rinse well with either more hot water or the hose.
Get a sack of wood flour, this is finer than sawdust, and you rub this into the feathers whilst they are wet. This helps to fluff the feather out whilst drying them.
When dry comb through the feathers.
If you stand the horse on a sack whilst using the wood flour you can reuse it as you go.
Once their legs were clean and dry I would bandage them from the knee/hock to the top of the coronary band.