I put my guys tail in a bag for the winter. Just make sure you don't neglect it by leaving it in too long without brushing it because you can always put it back in. Make sure you condition it very very well too so it doesnt fall out or overdry while its in a bag. Hope that helps!
I just use a normal human shampoo & conditioner.. I braid it and wrap it(with vet wrap) and then take it down and condition/ rebraid it every week.. some weeks I just put leave in conditioner in and rebraid. Some weeks I wash it before putting it up.. it all just depends on the condition of the tail when it is taken down.
I use the Cowboy Magic Detangler. Its pricey for the bottle but its really amazing stuff and will last you a LONG time. You only need to use about a dime size every time you use it and its not something you have to use all the time. It conditions, detangles and it keeps the hair really manageable. I don't know if you can get that in the states (im in Canada) but you can get it at the tack stores here. I wash his tail when needed but for the most part I just take it out of the bag, put some stuff in it and put it back up. You can use pretty much anything though for conditioner, I use the mane and tail shampoo/conditioner, its never done me wrong and its quite inexpensive.