The safest way to polarize a generator is to disconnect the Armature lead from the regulator connection, and flash it to the Battery terminal for a moment. Some people just short a screwdriver blade between the two terminals, but I've seen regulators damaged that way. It's safer to disconnect the "A" lead. Just a quick flash is all that's necessary, less than a second of contact. A properly polarized generator should develop about 2 volts at the Armature terminal with the engine running, and the armature and field leads disconnected.
Jerry