I made a rack out of brass model rail track, using stainless threaded bar to hold the rails apart at just the right spacing to hold the cases by the groove/rim. Hangers (made from wire coat hangers) hold the rails at the right height - one set for mouth up, another for mouth down. Then I switched to stainless tumbling.
The track is something like this:
http://www.tenmille.com/GScaleTrack.html
I hope the description makes sense; I'm not at home to post a photo at the moment.