I'm reasonably sure I've seen at least one of the "restore old things" channels using a kind of vibrating bath with abrasive material for getting rust off and/or polishing old pieces of metal. Like a static sand blaster, I guess.

[0] isn't one of them but at least I'm not entirely mad - it does happen.

[0] https://www.youtube.com/watch?v=7VyRGoq5EnQ "The Secret Shine: How Vibration Polishing Perfects Stainless Steel"