I took the blade out of the knife, covered the pivot and lock surfaces with duct tape, filled a powerade bottle halfway with a bunch of river rocks that I had smashed with a hammer to produce small-grape-sized jagged chunks of rock, added some brasso into the mix, put the blade in, and shook violently in different directions and at different speeds for about 10min total. I would shake it in sort of a centerfugal motion so that the contents were being forced to run along the sides of the bottle, then I would do that the other way, and then I would shake it sideways (as one would, say, maracas) - alternating whenever I got bored, raising and lowering speeds randomly.
If I was trying to put a finish on steel, it would have taken a lot longer - the paint is much easier to stonewash, though, and takes less time.
Be warned that this will ruin the edge. You will likely have to re-profile it afterwards, which I did on my Wicked Edge.