@ChickenCanoe probably has more experience with chickens than all of us put together as he is an instructor and knows what he is talking about. I have used the elevated cage method with good results and found that it generally takes about three days. I did take a shortcut this summer with one of my persistently broody BOs. I cooled off her breast muscles and nether regions with a bath in a cool pool, which she seemed to enjoy, before putting her into the cage. I repeated it the following day and then released her to forage with the flock. She did not return to her broody nest. I used that method again on a different hen, also a BO, with similar results. These three-year old BO and a third one kept going broody, however, and I eventually culled them for the freezer.