Finished piece of furniture?-strip finish first-spray bottle of warm water. Spray surface until saturated. Let rest a few minutes- grab a rack of nails (ones used in pneumatic nail gun) Start at end of board, leaning at a steep angle-drag nails across heavily, following the grain trace along nots/swirls in grain. Do several times then use stiff wire brush-heavily scrubbing the surface-it will cause the deep lines to sink even deeper and soften harsh edges. Allow the board to dry completely, then finish your raised grain texture.