I just really wanted to share with you a product that I have had a lot of luck with my horse and me. The name of it is, Mane 'N Tail, and it is a horse mane and tail shampoo and conditioner by the company Straight Arrow. They also sell other products as well, such as other variations and detangle sprays. I use this product every time my hoses need a bath. Whether it is the night before a show or on a sunny summer day after they got super dirty. Usually when they need more than just a rinse off after a ride. The shampoo I use all over their body to get the dirt and sweat off the horse. I do the mane and tail and all down the legs, but I avoid going around the face unless I am very careful and it looks like it may need it. The conditioner I put in the mane and tail, and then let it sit for a bit before I rinse it out. Afterwards, I should be able to comb through the tail and mane with very few knots or tangles.
This may be surprising to some, but I have also used this shampoo and conditioner for myself. It works well and I have never had problems with it. If you are interested in trying it out for you or your horse, you can get it really at any store and not just a farm supply store. I have seen it at Wal-Mart and target as well.