I have used a human paddle brush on my horses' tails for years, including the ones that show. Never had a problem with breakage. I have one whose tail is crazy thick and so long it drags the ground. If you pay attention to what you are doing, you will not break or pull out a lot of hair. You should brush a horse's tail the same way you would your own. If you had a huge snarl, you wouldn't just rip it out would you? No, you would take your time and untangle it. A little common sense is all it takes to use a brush properly.
"Keep a leg on each side and your mind in the middle"