DH and I vaccinated 70 chickens, from babies to adults, plus worming them orally with Valbezan and we finished before the hour was up. We went to the coop before the pop door was scheduled to open. Hubby went in and grabbed them one at a time and brought them out the people door to me. I injected them, administered the oral wormer with a syringe, and he set the chicken loose. While he went back for another, I drew up the vaccine and wormer and was ready to go when he brought the next one out. We had a little work table set up and a metal coal bucket to drop the syringes and needles in for burning later. It went much better than anticipated. I am a registered nurse and I am quite used to injections so that probably helped. Knowing that we had split the dose into fourths and could mix another if we needed to was a big relief but we didn't need it. I would recommend if your young man is skittish to find an adult to help so you don't have that additional issue to deal with. He may find it hard to hold them still and in the correct position for you do do the injection.
Good luck to you!
Good luck to you!