1st post here.
I age my wood by spraying it with spray on oven cleaner (aka lye soap). I use the Carbon brand from Wally world that comes in a plastic spray bottle but any brand should work. Spray it on the wood then after a certain amount of time rub white vinegar on it to neutralized it. The time will need to be determined by doing a test piece. Be sure and do a test piece as leaving it on to long will turn it black. Test time can range from 3 - 30 minutes depending on how dark you want it and the type of wood being used. This is the best way I've found to give it a truly 100 year old weathered look in less then 10 mins. Basically it causes the woods natural tannins to react and age similar to the way it would if it was being exposed to nature, just at a much faster pace. Once neutralized and dried it should be safe to paint, stain, finish, ext... Good luck!