I post a picture when I get home, but we did it two different ways, one on some shelves and one on a guitar.
Basically all you do is put down a base color (if you want it to look kinda like birdseye maple use a white/cream, but you don't HAVE to it could be any color) Then when that dries mix up a concoction of powdered burnt umber pigment, dishwashing detergent and malt vinegar (I forget the exact recipe and again, this is just so it looks like wood, you can use any color pigment you want).
On the shelves we took the burnt umber glaze and applied it directly to the shelves then took our fingers and tapped the shelves to make spots (tapping the wet glaze removes some of it leaving various amounts of the cream base showing). On the guitar I dipped my finger into the glaze and then tapped my fingers onto the guitar (which was old and slightly yellowed) leaving brown spots. I really didn't intend for it to come out looking like BEM but at least 4 people saw it and said "Dude, how hard was it to get that BEM veneer on there?" so I guess it did. After you get all the spots on it let it dry for like 15 minutes, then SPRAY a light coat of clear on it to "set" the finish (I'm saying this mostly if you're doing it on furniture, do NOT brush a poly coat on top of it the second the wet paint hits the glaze the glaze "re-wets" and smudges) . After that you just clear coat it like any other finish.