How you manage your broody is dependent on your setup.
You need enough space for her to work with and she should be set up in a ground nest and well grafted to it BEFORE you give her any fertile eggs.
I have a built in brooder with attached run in my coop that I now call the Maternity Ward as that it's what it's been used for the most. I installed a hen sized sliding door in it so she can come and go as she wants and her buddies and the rooster can come visit her when they want.
When you are working to graft the hen to the ground nest, you will need to secure her in the area with fake eggs in the nest as she may panic when you remove her from the nest went brood on and break. If she does she likely wasn't that determined as a broody in the first place.
When you first remove a broody from the nest they are in their broody trance and stay stuck in a sitting position until they snap out of it. When you move her off where ever she is currently setting into the plush ground nest with fake eggs she will hopefully just stay down on the nest. Making the incubation nest as plush and comfortable as possible in a semi-private, semi-dimmed location will help her graft faster.
I remove my broody hen from the nest each morning at the beginning of chores and put her out where the flock spends the day and give her a poke to snap her out of her broody trance. She typically tears off with her wings spread, stops to deposit her giant broody poop then preens, eats, drinks and if it's warm out, dust bathes for a short time before making her way back to her nest. This is when you need to watch her. If she starts on a path to the old nest, grab her and put her on the ground near the new nest and guide her towards it to encourage her to go there herself. You don't want to just plunk her back on the nest. She needs to see it and go to it herself. Once she returns to the nest on her own without needing correction three mornings in a row you can give her the marked fertile eggs you want her to hatch.
I continue to remove the broody every morning up until the morning of day 19. She has to leave the nest for food, water and dust bathing. It also keeps her interacting with the flock. You can inspect her nest after you remove her and take any eggs that don't belong there.
While she is setting, the entire flock needs to be switched over to chick starter, All Flock or Flock Raiser crumbles with a container or two of oyster shell on the side for the active layers. I feed this way year round as it's the best solution for a mixed flock and all types of situations when the excess calcium of layer feed is not appropriate.
The ground nest she uses should not have any lips on it that will prevent a chick from being able to get back in should it fall out. I had a chick die of hypothermia one night when it couldn't make the 2" jump back into the shallow box I had my broody in. That was a very sad sight that greeted me in the morning.
The mother will generally leave the nest with 48 hours (usually less) of the first chick hatching. That is why it's so important to remove eggs that were deposited in the nest after the initial batch is set. She will then take her chicks to scratch around in the brooder area. I have found that the mothers like to take a least a day to teach their chicks to eat, drink and scratch a little before taking them into the flock.
I use this baby bottle for mom and her chicks.
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(This is a bad example of a broody nest. It was whipped together quickly because the hen was persistent and I couldn't break her so I gave up and gave her four eggs to hatch.)
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Mom needs to stay hydrated while on the nest and during the hatching period she will drink more and pant to cool her body temperature down.
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When the chicks hatch, she teaches them to drink from it. I leave it up until the chicks are three weeks old and very mobile and there is little risk of accidents at the adult water fount.
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use my brooder area, (8' x 4') as this is now set up as a feeding/watering station for the rest of the flock, and once enclosed would not allow access to the run, or pen. I could set up a temporary partition fence around the existing box ? So many thing to do !!! 
