If he doesnt have too much white (like just socks etc) then we sometimes use chalk in the uk lol! If he has lots, I've read adding a blue plastic bag to the water you use to wash him with helps. Random I know but I think it works!
Scrub the white bits with a nail brush, hand hot water and some Fairy Liquid. Rinse well until yoou can see the skin clean underneath.
Towel dry then rewash with a blue shampoo, working it well in and leave for a few minutes to allow the stain to dye the white hair slightly blue. Rinse well and towel dry.
This is the bit that turns white socks int ultra white socks.
Using Curash baby powder mix it to a soft paste with some warm water. Scrub well into the sock with a toothbrush. Then bandage over. I use white hand towels and white or blue bandages. Leave bandages on until just before going into the ring, remove bandages and brush any excess off.