I was watching my neighbor do this on her horses the other day, she'd brush out the hair and then pull out the underside of the hair. The horses didn't seem bothered, but it looked like it would hurt to me! She said you should never use scissors for this. Why? Is there anyway to do it that would be less painfull?

I prefer the long and ragged look in my horses, but there are special razor combs you can use so you don't have to just yank out the longest hairs. I'm not sure why you aren't supposed to use scissors, but that is what I was taught also.