I have little experience with incubators, so I'll speak more of the hen!
Broody hens do most of the work, but still need help.
False starts: some broodies, especial younger ones, will sit for a day or two 'practicing', then give up on it.
'Helpful' flock members: Yes, broody hens will sit on others' eggs! But when a broody hen is sitting, other lazy hens will stop by, see her in her state and say "Oh, are you doing that thing? Well, since you're doing that thing ANYWAY ..." then they will climb in on top of her and drop off their responsibility with the mother-to-be. This can be disastrous for several reason: One, too many eggs. A hen can hatch up to maybe a dozen eggs ... your numbers may vary, size of the hen, conditions of the box, blah blah blah. More tragic still is the staggered hatch. Eggs dropped off by lazy flock members days after she's started sitting have little chance. There are many issues with a staggered hatch, so best to avoid it! Most tragic is clumsy hens climbing in and inadvertently breaking eggs she's sitting on!
Once a hen goes broody, and you want her to hatch, isolate her in a place where she is on her own, safe and dry, food and water available, and a little space for her to stretch her legs. She won't eat or drink much but she will need the food. Put up to a dozen fertile eggs laid on the same day under her, she'll hatch whomever's eggs.
As for the babies, good chicken mommies will dote on them and teach them right away how to scratch and forage. If your inclined to have your hen hatch babies, be prepared to keep the babies until fully feathered before selling or adopting them out.
I think the incubation and brooder process will give you better hatch rates and consistency and better controls over early diet, but if the chicks are for your own flock, I feel chicken momma's know better than human mommas and the babies will integrate faster and better than the ones born/raised in isolation
