I use a plastic colander purchased and used solely for separating brass and SS pins. I slowly dump the entire contents of the thumlers tumbler into the colander over a bucket, letting the water in first...then slowly pour the brass and media in. Too fast and pins start bouncing out. Then I rinse the colander and brass, still over the bucket, turning it over in my hands. After about a minute the pins are in the bucket, and the brass is rinsed. The colander gets lifted off and the brass set out to dry, The water gets drained slowly out of the bucket, careful not to pour out any of the media that has settled at the bottom, then the media and whatever water is left goes back into the tumbler and the lid screwed down.
If you wanted to drain the pins, you could get a mesh seive or even pour them onto paper towels slowly.
The colander works well enough for me that I haven't thought about spending more than the $2 it cost me. As long as you are reasonably careful you don't lose media.