First one must understand that there are different requirements for NEW Peening Media and In-Process Peening Media.

New Media is tested per AMS2431 5 SCREENS

In-process media is tested per AMS2430 2 SCREENS

There are different requirements for each. However, if you chose to always test your media to the as New Media, you would always pass the In-process test. Not necessarily a bad way to go but you are wasting a bit of time and wear and tear on your test sieves.

I'm not sure exactly what you mean by "graphing" in your first question, can you elaborate?

Personally, I use the two screen method but I changed the requirement to be 10% passing / 90% retained in my internal procedures. I track the data in Excel, this way I can see if a trend is developing and change the screen(s) in the peening machine before it becomes a specification violation. If you do this, make sure you word your procedure in a way that explains this is a preventive action and not a hard requirement trumping AMS2430.