Ramsi,
A trick that I have seen used in the past is to soak the brass in “Liquid Plummer” drain cleaner for 10 to 15 mins. Pull the parts and let dry, then rinse. As long as the brass is not coated with a finish to perevent patina this will make the brass look old.
Good Luck,
DOne this a few times , looks great. Sorry it is late in posting but had to find the article .
Brass:
Soak in lacquer thinners to remove protective coating (overnight).
Suspend ABOVE ammonia in a jar containing same. Don’t let the piece come into contact or it will mark in an undesirable way! This can take as little as a few hours for a light patina, or overnight for a dark blackish look.
Keep a eye on the brass to see when to remove it.
3)If the brass hardware has a thin plating, after 2) scrub it off with 0000 Steel Wool and do the ammonia thing again.