I've often thought about using those rubber stoppers to get the inside of my brass clean. I figured to fill it like 1/2 way with tumbling media and then put a stopper in. Would clean everything but the neck.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.