The blue stuff I use is called Blue-Kote, I bought the pump bottle and the sprayer dosen't work for me. Cotton balls. IT STAINS! I had DD hold a hen, put it on her comb and she shook her head like a dog. DD and I had blue speckles on our faces for a few days. It was summer and we have a pool. DAYS! Rubber gloves and watch out. I would put the hen in at night and try to be out early in the am when they all wake up to keep an eye on things. Good luck!
I have not had good luck with blue kote for pecking and have had a similar experience with the pump bottle. The spray can works better and is worth a try.