There are shampoos out there that are specific for coat colors; a good one I really like to get the white clean is called Quic Silver but as indicated, do not leave this on long. It is purple in color and can color the hair. If you use it, dilute it in a feed bucket full of water, use a sponge to get it on the coat, use a soft bristle curry or washing mitt to scrub and then rinse. Do one side of the horse at a time.
I have always had dark bays so use this on socks and such and have left it as long as a few minutes without any issues but have never used it on a mainly gray/white horse. When using it in a mane and/or tail, wash and rinse immediately..repeat if necessary. In that case I would use a regular shampoo first to get the mane/tail clean and then do another wash with the whitener to get it white. If you don't want to use an actual equine shampoo for the whitening, you can dilute a few drops of plain washing bluing in the shampoo water (as in put shampoo in a bucket, fill with water, add a few drops of the bluing and swish it around to dilute) of whatever you are using..do not use this directly (as in undiluted) on the white or you will get "ink" spots :) I always use a conditioner/detangler on the tail afterwards to help with, well, detangling and make it silky.
Unless the horse is very calm, do not use soap on the face. Use a wet sponge and go over several times to get the dirt out. If you use soap and can't get a good rinse you will leave a residue which can make some horses itchy.
Microtek has a nice line of shampoos as well from basic to medicated for things like fungus control.
As for Show Sheen, haven't used that stuff in years as it really does slick things up. I used to use it only below the hocks and knees to keep socks cleaner but otherwise left the rest of the body alone.
Last edited by tlkng1; 07-23-2013 at 12:44 PM.