In fact there are two main methods of selecting Back Course on jets. On Boeings the pilot sets the normal (front) course on the Flight Control Panel and the Flight Director compares this with the aircraft's current heading - if it's more than 90 degrees you get Back Course. On other systems, such as most Collins APS or FCC, there is a "BC" button that must be selected by the crew as part of the approach procedure.
BTW, there's at least one other country that uses BC mode, the government airfield at Beijing apparently utilizes the back course from the International airport.