Interesting way to clean a motor filled with dirt from a crash. Thought they were kidding when they told me.
Well, they do work underwater just fine, it's just the main electronics, your flight controller and ESCs that need to be protected really.
I will never look at flying in the Rain the same way again I have a lot of spare parts. Maybe I will put together a water resistant one out of mostly spares for fun.
Just wondering, I see people use good quality oil to lubricate the shafts. How about using a tiny dab of bearing grease? A very light coat would stay on forever. Is that overkill?
You can get water repellent spray to waterproof PCBs etc, or just make a watertight frame like these guys: https://www.swellpro.com/waterproof-splash-drone-3-auto.html I think it's not recommended to put grease on the motors anywhere.