I have done this mod on my reverb model.
The reverb footswitch jack is a TRS jack, but only the tip is used. All you have to do is connect the wire as shown in the above picture from the switch to the ring on the reverb jack. You will have to get another footswitch ( a dual switch w/ a TRS cable) or I just changed the end on my current footswitch (the Reverb plug) To a TRS plug and connected the hot wire to the ring ( You will not be able to switch the reverb on and off). But my plan is to get a four button switch that I can leave on my pedal board, and switch everything.