I use zip ties and I love them. I changed them every few weeks until the hens were full grown. Now my hens are about 8 months, and their legs aren't getting any bigger, so I don't have to worry. You just pop them on, make them just a little too small to fall of when the foot is limp and snip off what's hanging off. Keep a list of who's what color, eventually you can remember. Like, I know our barred rocks are, Green band - Felene (it rhymes, green-felene), Yellow band - Felicia, Green Band - Fiona (green like Shrek, Fiona is his wife)
=] Wouldn't work if you have more hens than colors though...