Three of the popular items for making your own "Forced" patina are: Mustard, some say the "grainy" kind works best, I'm sure they mean spicy brown type. Ketchup works as does Vinegar. Oh I have stuck a small blade in a potato and left it over night. Just be sure and neutralize it will after what ever you use. I have heard that windex will neutralize these materials I have listed.

And Just "BLOT" it on, or smear it but DO NOT try and get an even smooth coverage. The Uneveness is what makes the finish look good. And don't be afraid to coat, clean, dry and then coat with another material, filling in the areas you left open the first time.