I used a screwdriver because that is what I had on hand that was long enough to get past the power tubes and to reach the front face plate.
Trick, use a flashlight to view the front window, if you are resting on the tool on the bottom or on left or right side of the front main board, that will not budge.
The window is an odd shaped section on the front main board (this would be a baffle board if it was a combo) (almost a U or D shaped opening that is between the power transformer and the output transformer) and a light shinning in to the cavity will help you see it. Your screwdriver, dowel rod, board or what ever you need to use to tap the front plate away from its position must be placed in the window, not on the bottom or far right or left. You almost have to place it between the power tubes or just under them and tap it a bit. The piping surrounding the front face plate does make it a tight fit. It took a little effort for me to get the front cover off the first time. Try not to hit the power tubes with anything.