What are you looking to do exactly? Do you have a picture of what you're trying to achieve?
If you just need to create a faux wood grain, that's fairly simple:
First thing is to fill the seams. screw holes and all the other non-realistic markings (sand off TMs, etc).
Next, hit it with a coat of primer. Mask off the parts you want to look metal. Then spray it flat black.
Next get some interior latex paint (off-white) and a very stiff bristle brush (about 1" wide). I found the best way to make a stiff bristle brush is to dip it in the paint, wipe off as much paint as possible and let it dry overnight. Sparingly, brush the latex over the gun (in one direction) allowing the black to show through. This is creating your wood grain.
Get some spray-on wood stain (I believe minwax makes one as well as other companies) in different shades. Usually colors like light walnut, mahogany and cherry wood give the best results. First spray a coat of the light walnut and allow to dry. Figure out what areas would see the most handling (generally the center of the grip). Since this area would see the most action it should have the lightest coloring. Now from there, spray on the mahogany (leaving the light walnut to show through in the grip area and anywhere else there would be wear (maybe where it would rub on the holster)). Once that has dried, blend out into the cherry wood (you're going for a fade effect here with the paint). Finally, after the cherry has dried, spray a little of the flat black along the edges and corners to make it look like years of gunk build up.
After that has had a day or so to dry, remove the masking from the "metal" parts and mask off the rest of the gun (use low-tac blue painter's tape). Use either aluminum or brass from krylon (depending on your tastes) and use a little bit of thinned black acrylic as a wash. You should end up with a pretty authentic looking piece.
Hope that was what you looking for...
-Fred
