I use Eqyss conditioner/detangler. I find that mane n tail only really works when it's wet, and then when it drys it leaves a residue. I try not to use too many products...I'm afraid they're going to cause more harm than good, and they can get expensive.
I just give it a good wash, and instead of using wash out conditioner I just run the Eqyss through it. It lasts a lot longer than other conditioners, and you can use it wet or dry. It's kind of expensive, but it lasts a lot longer and you don't have to use it as often.
My guy has a huge tail, but his hair is really thick and it's not very "good quality"... doesn't really flow it just kind of hangs there. The eqyss is the only one I've used that conditions it, makes it super soft, and seems to make it LIGHTER and more flowy. It also prevents breakage, and adds a nice shine
(You can use it in the mane too just to make it look nicer and feel softer)
Make sure that each time before you brush his/her tail it's thoroughly conditioned. Start at the bottom and work your way up, and wherever you feel you can't brush through it without ripping it, rub in a little conditioner and work it out with your hands. (Once you do it once, and keep up with it, it will be easier every time) By starting at the bottom you can make sure you get out all the knots to prevent breaking it, and you can make sure you can get all the knots out without missing any
Also, I would use a good tail comb/brush instead of like a stiff or dandy brush, I find those just rip pieces out of the knots to get rid of them, instead of just untangling the hair.
OKOK I know that was really long, but I've become a PRO at maintaining tails and manes haha (well, not really a real PRO, but you know what I mean)
PS, here's what my guys mane and tail look like after the Eqyss...I know his tail is broken on the left side...but he rubs on the fence after I ride because the sweat under all that hair makes him itchy :-0
PPS, sorry that was so long :-X