Step one: take some steel wool and put in a jar and cover with vinegar. Let it sit at least 24 hours, the longer the better. (I expected the vinegar mixture to turn black or something but it didn't.) after 24 hours Step two: make a strong cup of tea. I used Chai. brush the tea on the wood and let dry. Step three: brush on the vinegar mixture.
This is an easy 4 step process from taking freshly purchased wood from the home store to look like weathered old wood thats been around for ages. All you need is some paint, stain, and sandpaper. Go here to look at the tutorial: