The patina is created by the surface of the brass reacting to it's environment. The metals in the brass bond with stuff, like air, and the patina is helped by acid, like is found in your sweat. To polish brass you need to remove the metal that has bonded with other stuff. Most of the polishing action is just scraping it away with an abrasive. Some cleaning is done with chemicals that react with the metal. Whenever you polish you will remove more metal from high areas and less from the low areas, the engraving. Over time you will wear down the top down to the level of the engraving.
Lacquer will stick and it will protect brass, and other metals. The problem is that it is soft and will scratch/chip. That exposes the brass and it will tarnish where it is exposed. It will look like hell and you will have to polish, scrape, away the lacquer and apply again. If you just apply new lacquer over the scratched lacquer you will be able to see the scratches.
Aluminum and stainless steel also patina. Aluminum forms an aluminum oxide coating that is clear and any scratches reform the clear coating. In stainless steel I thing the chromium migrates to the surface and also creates a clear coating.