Sooo complicated!Sooo many complicated methods and magic potions.
Bung your brass in a cloth bag, stick it in the washing machine on a 40 degree wash, empty bag onto tray and place near fire or radiator. Job done.
ps
make sure the bag neck is well secured and that the boss is defo out well beyond the end of the cycle. Wot could go wrong just might…..
0000 steel wool. 5 seconds per case.
Admittedly, this method is defective in that it doesn’t involve a machine or gadget.