Gina Carano underwent a six-week intensive tactical training course with Aaron Cohen, an ex-Israeli special ops fighter. She spent three hours a day in stunts and three hours a day with Cohen. During a particularly harrowing two-week period when Cohen was teaching Carano the art of surveillance and countersurveillance, he and his team tracked her via a GPS system installed in her car. He gave her a prop blue pistol to use as defense and intercepted her as she was coming out of a hair salon. "I just got extensions and was feeling so pretty and there he was," recalls Carano, laughing. "He taught me entry and exiting a building, clearing a room, he put a GPS on my car, he like, followed me around. He had me stalking people, he had people stalking me. They just put me with a soldier who had never done a film before either. We were just soldier and a fighter thrown together in these unique circumstances and got to know each other's backgrounds. I think that was the biggest part of my preparation."