Since everyone has been going on about getting a white tail white I thought I would just add my very simple, but effective tail cleaning treatment.
I have a grey horse so I always have some kind of whitening shampoo, then I also always have regular horse shampoo.
My horse's tail was nasty before the clinic I went to this last weekend. Since I hadn't shown or anything for a few months due to winter break his tail did not get washed so it was no longer white at all but a brown and yellow color
Too wash the body I always mix both the whitening shampoo AND the regular shampoo in a bucket of warm water (I also add in a conditioner but it isn't needed). After wetting the horse down I dunk the tail into the bucket of soap mixture. I hold the bucket up for a bit, swishing the tail a bit, then I take the tail out and with my mitt and hand I scrub it (as if you were rubbing your hands together). The hairs rubbing against each other creates some friction to help remove dirt and grime yet it doesn't tangle the tail up anymore. I then dunk the tail again and repeat the scrubbing, making sure I get right down to the tail bone.
I then use straight whitening shampoo. I put some on my mitt and starting from the bottom I work it in. I work in small increments making sure that the shampoo lathers up totally white with no purple residue left (don't want a purple tail). Once I cover the whole tail (using the same scrubbing action as before) I leave it to sit while I wash the whole rest of the horse (with the soap mixture).
I then come back to the tail and dunk it in what's left of the mixture in the bucket, then scrub. Then I use the whitening shampoo again.
I then use the whitening shampoo on his white socks and I rinse the whole body first (to allow for the tail to sit even longer in shampoo) then rinse the tail at the end. While it's still wet I put in the leave-in conditioner, then spray in some showsheen (yes I am terrible and still use show sheen).
What I am left with is a totally white tail from tail bone to the tips. I did not know if I would get that tail white again it was so bad but in one wash it came out sparkling white.
Now if his tail was normal dirty (like it would be during show season) instead of atrociously dirty I would not have done the extra scrub at the end with the straight whitening shampoo, but with how dirty it was I really wanted to make sure it got clean.
It seems like a long process but once you are used to it it only takes a couple minutes and you are never 'waiting' for it to sit as you are always busy washing the rest of the horse.