You're on the right track.
Metal polishes from a jar remove tarnish, but they don't do much for microscopic pits. That requires buffing.
Get an 8" sisal wheel and a bar of aggressive emery compound. Mount the wheel on your 3450 RPM motor and have at it. I seem to recall that yours is a 2HP motor, which is about right for this job. My buffer is a 2HP 3450 RPM motor.
Wear welding gloves, because the workpiece will get uncomfortably warm very quickly. Wear full facemask. Be careful to never present a leading edge to the wheel, because if you do the wheel can "grab" the workpiece and make it a high-speed projectile. (Surface speed of the wheel is about 82 mph.)
When you get done, that wrench will look like it was chrome plated. For some reason, highly-polished steel resists rust surprisingly well.