Using the large paint brush, paint an even base coat of yellow ochre colored paint onto your plywood. Allow this base coat to dry fully before continuing.
Apply a layer of gel stain over your dry base coat with the paint brush.
While the stain is still wet, drag a fine wood-graining comb through the stain with even fluid motions. Begin on one edge of the plywood and pull straight to the opposite edge. Begin next to your first drag and repeat until you have laid down a preliminary grain over the entire piece. Allow the stain to dry completely.
Paint on another layer of gel stain.
While the gel is wet, apply "heart grain"--grain created from wood at the center of a tree or branch--intermittently over parts of your plywood using the wood-graining rocker tool. The Painting and Decorating Concourse describes two ways of using the rocker tool; the half rocking motion and the full rocking motion. For the half rocking motion, start with the handle pointing up completely perpendicular to the board. Simultaneously rotate the tool down and pull it toward you to create the grain. The full rocking motion is completed in the same manner, but after rotating the tool down, rotate it back up as you continue pulling toward you.
In the areas of your plywood board where you did not apply heart grain, comb through the wet stain with the a graining comb. There should be more straight grain than heart grain for the most realistic look.