Sand the surface of the plywood with a fine-grit sanding block. Make sure you are using the smooth side of the plywood and not the rough side. The surface should feel smooth. Wipe away any remaining dust with a damp cloth or a tack cloth.
Stain the wood with the desired color of stain. Paint on the wood stain, going with the grain of the wood. Let the first coat dry for at least six hours. Rough up the surface lightly with the sanding block and apply a second coat if necessary. Let this dry again for four to six hours.
Apply a clear coat of polyurethane over the stain with a paintbrush. Go with the grain of the wood. Let the poly coat dry for at least eight hours before hanging the wood.
Sand the surface of the plywood with a fine-grit sanding block. This will rough up the finish enough to allow it accept primer.
Apply the primer to the plywood with a paint roller. Apply the first coat and let it dry for at least four hours. Apply the second coat to thoroughly hide the grain of the wood. Let this second coat dry for four hours.
Paint the surface with a roller and latex paint. Use the color of your choice and apply one coat of paint. Let it dry for four to six hours and apply a second coat.