When I have a broody I wait until she's been in the nest most the day and all night for 2-3 days...along with those other signs I posted.
Then I put her in the broody enclosure with fake eggs in the floor nest, she won't like being moved, but if she is truly good and broody she will settle onto the new nest within a half a day.
Then I give her fresh fertile eggs and mark the calendar.
I like them separated by wire from the flock, it's just easier all around.
No having to mark eggs and remove any additions daily, no taking up a laying nest, no going back to the wrong nest after the daily constitutional.
I remove barrier about one week after hatch. The chicks are usually safe it's the broody who has to 'fight' her way back into the pecking order...which can be quick or take a few days.
Lots of space helps for re-integration.