i think the broody knows when it's getting close to hatch time. i've watched mine do their own lock down and not move. One of my broodies will let me hold a plate of food and then water up for her to eat and drink, but the others won't. My broody Juliet just hatched seven little babies. She would not get off the nest for the last five days. i was worried about her, but she was fine.
My suggestion is to not mess with them as the hatch is going on. It could take a couple of days. i've never had a chick get squished. i've watched the moms pushing them back under with their beaks if they try to come out from under too soon. Worried about that the first time, but since i've seen it several times now, i guess they know what they're doing.
As the hatching goes on, i will check after a day or so, gently reaching under to pull out any broken eggs. After two days of hatching, i may reach under and pull out any unhatched eggs, gently tap and chirp to see if there is a viable chick inside. You will want to take away any un-viable eggs by about the third day so she will get up and start teaching her chicks to eat.
Good luck! There is nothing sweeter than a new mom with her baby chicks!
