Prepare the wood surface to be painted. Fill any holes, cracks and chips with wood filler and sand the surface with a fine-grade piece of sandpaper.
Apply a coat of latex primer with a roller. Allow this to dry thoroughly.
Apply a base coat of the main color of your granite and allow this to dry.
Dab your natural sponge into a lighter shade of your base color paint and dab on the paint, using a light pouncing motion. Allow this to dry thoroughly. Dab another color over some areas of the surface. Remember, granite is not uniform in color.
Dip a small paintbrush into another color and flick the paint over the surface, by using a quick wrist action to flick the brush. Allow this to dry, and repeat this process with another color of paint.
Dip an artist's fine-tipped paintbrush into another color and paint faint random seam lines. Allow this to dry.
Apply a coat of polyurethane sealer over your finished granite surface.