I've had great luck with the wire-bottom cage broody-breaking method. All of my broken broodies returned to normal life in about three days time, none the worse for wear. They were back to normal egg laying within two weeks. I saw no evidence of damage to their reproductive cycles, in fact, three of my hens love to go broody every six weeks, almost on the clock.
I've tried other methods of breaking broodies, having them sit on ice packs and giving them cold water soaks, but none worked. If you add a fan and have it blow under the broody cage so as to flutter the broody's feathers, she will get un-broody quicker.