Marine grade plywood is plywood constructed without any gaps and voids. Its layers are laminated together with waterproof glue, which is not affected by exposure to water. Marine grade plywood is commonly used on boats. Although pre-stained marine grade plywood is available for purchase, you can always stain it yourself.
Sand your marine grade plywood down to raw wood using your electric sander. Work slowly and use even pressure while sanding to ensure a clean surface.
Wipe the excess sawdust from your plywood with slightly damp paper towels.
Allow the plywood to dry for five to 10 minutes.
Apply a liberal amount of stain to the entire side of plywood you want to stain using your paint brush. Always stroke your paint brush in the same direction to avoid streaks.
Wipe the excess stain from your plywood with clean cotton rags. Work quickly to avoid spotting.
Allow the stain to dry for at least one hour before applying additional coats of stain.