Hello,
I restore a lot of brass trim. Almost all the brass I've encountered was originally lacquered but the lacquer has expired so tarnish has formed on the brass underneath it. Once the old lacquer has been removed using Nitromors or a solution of vinegar, hot water and washing up detergent, polishing the brass is easy, I just use Brasso. I always relacquer polished brass with Rustins cold metal varnish sometimes mixed with M&P dark gold lacquer to darken it slightly. I will try the quicksilver solution though cos vinegar takes a while to work.
Howard