You don't. Alteration of a rabbit's coat per ARBA are grounds for DQ as rabbits are to be shown in their natural state. Dying, plucking, cleaners are a NO NO.
I have seen others use stuff, but that doesn't teach or do good. If I win, I want my rabbit to win. Not because I used an expensive grooming coat spray. Some breeds, grooming can ruin a coat like that.
Now if you are talking about trying to get a lil yellow off from stain pee, that's not the same thing as alteration. White vinegar and baking soda rubbed on and brushed dry. Some use peroxide, but that dries and damages coat.