Put hand and semi-auto in small plastic bag.
Fire at will.
Remove hand and brass is in the bag.
Remove hand and brass is in the bag."
Yeah -- riiiiight...
Noob, have you ever fired a handgun, specifically a semi-auto?
Go ahead, put your hand in a small, gas-tight bag with a handgun -- and fire it. Then get back to us on how your hand feels/looks...
Also, my P7 tosses all its brass in a one-yard circle ten feet back and to my right -- so I put down a plastic tarp to save picking the brass out of the grass.
When it landed, the brass was still so hot it melted through the tarp. Ruined my brass -- and the tarp.
Good luck with that plastic bag idea! Let us know how it works for you...