In this photo you can see the trigger (for cannon) in the firing position after being rotated 270 degrees; there it contacts a small firing button set into the upper front of the grip. At the same time, the topmost button (for MGs) is exposed. To fire all weapons, together, the index finger pulls the trigger, while the thumb depresses the top button. I hope this makes sense.

And the PTT button is under your little finger so if you are in a turning fight trying to fire both cannon and mg’s together and talk to your wingman at the same time all you have to control the aircraft with is your two middle fingers and the palm of your hand, decidedly unfunny I imagine.