Another vote for the clothes washer, but NOT the dryer.
Before I got a tumbler MANY years ago, I'd put a few hundred cases in a cloth (mineral sample) bag, pour in some powdered detergent, tie it closed, and run the bag(s) through a complete wash cycle. They'd come out with a nice "matte" finish and very clean. Spread 'em on a towel in the bright sun for a few hours, and evenwhere we lived in the far North, they'd be totally dry.
Here in Nevada, now....they get so hot from direct sunlight that I'd have to watch out for burns!