As afar as "aging" metal, I don't know how professional restorers do that. I make gun racks, coat racks, antique-looking boxes and stuff to sell at an antique mall. My "aging" process is an old wooden box that sits out on the patio 24/7 - 365 filled with metal parts of various types and dubious origin. Mama Nature and Jesus ages my stuff nicely. Wire brush, buffing wheel, few whacks with a rock ...new metal looks old.