Moldy wrote:
... Why are you using vinegar instead of actual copper or brass polish out of curiosity? Wouldn't 5min with a rag and some polish be easier? ...

I used 2014 to 2021 Isopropanol, a soft slow rotating brass wire brush and very very fine sandpaper to clean mech mods INSIDE.
But that needs 30 min for each mod.
To find a faster solution, I put the question in post #2.
In post #3, #5, #18 and #19 the answer was "vinegar".
I tried that, and yes, for pure copper, pure brass and pure SS, vinegar seems OK.
But vinegar destroys chrome plated springs,
and perhaps painted tubes, plastics, aluminium and silver plated contacts.
I am not talking about, how to make a mech mod outside very shiny.
Seems kerosin or kerosin mixed with car fuel could be a solution.
But in the next step, I will try Zarcks post #12 solution with the ultrasonic cleaner.