I'll ask my daughter, Michelle. Her twin boys are thirteen now. She kept it short for a long time, but now they seem to like it a little longer and care for it themselves. Looks as though you've got plenty of good answers, but I'll still ask her what they use.

I have very fine hair and have had to use the start-at-the-ends method as JohninKS described since I was a kid. Used to cry my eyes out when my mom combed it. We didn't know as much back then, so it was a fine-toothed comb top to bottom and it hurt!:-)