If it's a clean polish you want without the need for elbow grease, a metal vibratory bowl (or tumbler) should be on your radar. Not to be confused with a vibratory feeder, which Google will spout ...

Such contraptions are known as, unsurprisingly, rotary rock tumblers. But what [Fraens] has put together here is a vibratory tumbler, which…well, it vibrates. If this was Rockaday we might go ...