Smart sister you have there. This site is full of very knowledgable people and most will respond very quickly and share their experiences. Your never alone on BYC that's what I love about it.It says 20-22 for the vaccination itself. However, I think I'll probably use the TB as it's small and manageable.
I love BYC. Otherwise I'd be all by my lonesome in this! NOBODY I know has chickens. Except now my sister, who is a newbie of 2 weeks. And was smart enough to get big fat chicks that the hatchery vaccinated for her.
Hens go broody when you don’t want them to… and won’t go broody when you do. 