Hi K.! My son had a doc band for three months earlier this year, we were very happy with the results! I'm a busy working mom and knew I couldn't free hand paint it, so... I went to Hobby Lobby/Michaels (can't remember which, but either one is fine) and just bought some really cool stickers. I got one package of cute little quotes and one of "boy" stuff like footballs and such. Then I also bought a bottle of the mod podge. It was SO easy and I got tons of compliments on it! (wish there was a way to send you a pic?) I just put the stickers on the doc band and then painted the mod podge over them. I let it dry overnight, and that was it.
Depending on how mobile your daughter is, and how long she wears it, you might have to replace some stickers if they start to peel. In that case, just take rubbing alcohol and rub over the sticker you want to remove. Replace with new sticker and re apply mod podge in that area. You can also redo the entire helmet if you want a new look. Just a little alcohol takes the mod podge and stickers right off.
Hope this helps! Good luck!