Correct, the paint doesn't adhere to the plugs great but well enough in my opinion. I believe that's how it was originally done anyway. You could primer them and then repaint them an off white like the original color but, it works well for me to practically weather them by scratching off the paint easily to match screen references. Then I just applied a clear coat. Called it done.
Excellent. I think you're right; that's why the screen used seems to have so much paint coming off. To be honest the whole thing looks like it was fairly rapidly thrown together. They just stuck a tube in an existing gun and glue some bits to it.
I seem to recall seeing a thread where someone had identified how to add the extra holes to the MPP that don't seem to be standard to the units from the factory but can't seem to find it.