I would advise giving the horse a dock clip if you're up to it. My horse has a pretty thick tail but the hair on the sides of his dock are cut short so there is less to deal with. Also, you may want to cut the bottom of the tail shorter so it isn't dragging on the ground. If the tips drag on the ground they are likely to get muddy and tangled and gross really quickly. Cutting the tail shorter will also be safer because she won't be able to trip on it or anything. Finally, buy a good detangler (I use mane & tail) and spray it on the tail, then brush it in sections starting from the bottom. Hope this helped.