I have a coop that has a large people door and also has a cover over the nest boxes. I open the door and the nest box cover so that its very light in the coop. If that doesn't work in a day or two, I lock the hens out of the coop for a few hours and place the broody hen out side also.
I have let the silkie ( my most broody hen) raise two chicks I got from the farm store this year. Worked out great. But I wont be able to do that again as I have no more room for extra hens. She is sometimes hard to break from being broody, seems to be broody about 4 times a year. So if the above methods don't work I will also let the hens free range out of the chicken yard. That isn't something they do very often. I need to keep the rest of my yard looking nice. So I open the gate at around an hour or two prior to dusk, and she is so excited to be in my garden that she stops pacing trying to get back inside the coop.