I haven't been that lucky on my one try to get a broody to foster. I agree that you don't want a light, even a red one, when you put the chicks under the hen. Ok so you need to see; take a flash lite and cover it with a cloth or something so you can see a little. My chicks were ordered so they arrived on day 3. I had set up my broody in a nice big nesting box inside a large cage several days ahead and she had settled back in on some infertile eggs. As soon as I got home with the chicks late in the afternoon (at dusk), I went into the barn with the chicks I had a heat lamp on so I could see and put the chicks under her. They melted into my broody's feathers like butter on a hot biscuit. It was magical. But any chick the hen could see, she would peck. Hard. This hen had hatched and raised a single chick before and is constantly broody; a buff Marans. I regrouped my chicks in their box, turned off all the lights, waited about 30 minutes and using my dimmed flashlite as little as possible, put the chicks back under her. You don't really have to put them directly under her because the chicks will go straight into her feathers. I thought all was well but in the morning when I turned on the lights, the hen started pecking the chicks hard. I quickly removed them.
I spoke to a friend who has successfully transferred 3 day old chicks under broody hens several times. She also said turn off the lights as much as possible and slip the chicks in. My hen had been broody for weeks but my friend has put them under some hens that have been broody for only a short time. You might keep the lights dim for the next couple of days until the hen starts to move around. I asked what she has noticed about fostered chicks vs. hatched chicks. She said the foster chicks are not as responsive to mama's signals as hatched babies who start communicating with mom before they hatch. Interesting.
Good luck and let us know how it goes.
Relax
Breath
