scratching the surface is accomplished by taking a wood float and driving in some small nails on the underside and leave the heads protrude slightly, a dozen or more should do the trick.
directions for use--
After you are happy with the surface just take the float and make a few passes in a circular motion all over the surface that is going to get another coat. The scratches will give the next layer something to grab ahold of rather than a smooth surface.
NH
