Here is a video about how to “relic” guitar parts for that aged vintage look. This is the way I’ve been doing it for a number of years with great results. It’s best of you do this in a well ventilated area and wear rubber gloves. After you remove the parts that you want to age let them sit for a while on cardboard or something similar. Check them in about an hour and rinse them with water. See how they look and if you want more aging then put them in for another round. Cut the time for gold hardware down to 10 minutes and see what your parts look like. Gold will age faster than nickel and certainly chrome as well as stainless steel.  Please feel free to ask any questions and leave me some comments on how this works for you.