Many of the brass sprayer I get are in covered in a dark gunge – that’s how I buy cheap! I have occasionally brushed on brick acid to remove thick mess, but quickly wiped it off before it causes damage to the metal. It’s quite effective and time saving. Most of the time I use polishing mops and paste on a bench grinder. You do have to take care with the manufacturers names plates as the harsher pastes can rapidly cause wear!!
Finer grade wire is also useful.
I do not use polishes like Brasso etc as the brass appears to revert back to dull very quickly. Brass also reverts back very quickly the more it is exposed to external elements (so they stay in my shed).
My view is that as most of my acquisitions are in a mess, I clean them back to original but they will ultimately dull down naturally. I am not going to then spend my life continually re-polishing. They will have to develop a natural patina but without being exposed to chemicals and the open elements.
Not everyone will agree but that’s broadly how I work.
.
