Run a damp cloth over the surface of the plywood. This contact with water can cause the grain to rise so that it can be easily sanded. Sand the raised grain, if any, with 120-grit sandpaper. Lightly sand the surface of the plywood with 220-grit sandpaper. Remember to sand with the grain of the wood and not across it. Clean the sanding residue off the plywood by using a rag soaked in denatured alcohol.
Prime the plywood using a 3/8- or 1/2-inch nap paint roller.
Sand the primed plywood using 220-grit sandpaper and remove the dust using a denatured alcohol-soaked rag.
Apply the first topcoat of paint using a paint roller with a 3/8- to 1/2-inch nap.
Allow the paint to dry according to the manufacturer's instructions before applying the second coat. This can range from two to eight hours, depending on the brand of paint used.
Apply the second coat in the same manner as the first. If desired, you can sand between coats using 400-grit sandpaper.