Ball bearings are great for paint agitators too.
Don’t put them in a glass paint bottle/jar. though.
Revell used to sell
airbrush-ready paint in glass jars with a ball bearing already in it, and I had two of them break in my hands as I was shaking them. Luckily I didn’t cut myself but having paint suddenly fly everywhere in my hobby room did not exactly improve my mood … After that, each time I opened a new jar, the first thing I did was fish out the ball bearing.
As for cleaning airbrushes: I bought an Aztek precisely because of my dislike for cleaning the things, and the plastic insides of one of those are a lot easier to keep clean than the metal of the Badger 150 I used before. When I’m done spraying, I put clean tap water through it until no more paint comes out, then put it into an ultrasonic cleaner, with a dollop of ultrasonic cleaning fluid in the water, for ten minutes, and finally give all the parts a quick scrub in lukewarm water in the sink, using a pipe cleaner and a toothbrush. (I take the nozzle apart a bit by pulling the outer sleeve from the inner one, something you’re not supposed to do according to Testors, but it makes it easier to get the paint out so I do it anyway.)
Note that I don’t tend to spray enamels, largely because you can’t clean them up with water.