After the firing pin is pushed forward out of the way, you should be able to rotate the plug down (if needed) by pinching it with your thumb and index finger, and turning it downward.
If the firing pin is fully forward and completely out of the way, the plug should push straight out, without having to turn it down. There is a plunger and spring in there.
I hold the firing pin fully forward by clamping the tip that is extended out of the breechface with a hemostat.
Carter