I don't have that problem with my current horse, her mane is almost too silky, get tangled soo easily, but I refuse to trim it as she's an Arabian. With horses in the past, I use a very concentrated conditioner human works just as good as horse stuff. I wash gently, with soap, then rinse and put conditioner in. I normally do this while I'm washing the legs of the horse, so the conditioner has time to set, but I'm still doing something, cause I get bored easily lol. Once I'm done with the legs, I rinse the tail out, then use something like cowboy magic if it is still a bit tangled, and I brush and braid the tail, and then I put it in a tail bag to help keep a lot of dirt from drying out the tail. I will take it out every couple/few days, and use more cowboy magic, or show sheen (I prefer cowboy magic) brush it, and then after riding or whatever I'll rebraid it and bag it. The night before a show, I make sure that it gets nice and conditioned, and again I'll bag it. I like to get to the barn early before a show to do last minute touch ups, and I'll unbag the tail, rinse it a bit, I personally don't like the frizzy been braided forever look, put a little more conditioner in, and do a light brushing.