You can also use Mercury Transmit to send video frames to external video devices. You can continue editing on your primary monitor with full screen enabled. Got a second monitor? Simply drag the Program monitor window to it and when you toggle full screen, it will display on that monitor. Or you can also use the Shuttle Keys J (Shuttle Reverse), K (Shuttle Stop) and L (Shuttle Forward) to play your video.
The ` (Accent key) is typically located above the Tab key or just left of the numerical 1 on the keyboard.