Lay out newspapers around the cabinets. Remove all hardware using your screwdriver, including the hinges. Lay out the doors on the newspapers.
Load the pad sander with rough sandpaper. Sand all of the wood surfaces, taking off the finish and exposing the wood. Vacuum the dust.
Re-sand the surface with medium sandpaper on your sander, removing the last of the finish and completely exposing the wood. Go over it a third time with fine sandpaper in the sander to smooth out the surface. Vacuum the whole area well.
Apply wood stain over the pieces using a paint brush. Lay the stain on heavily, letting it pool on each surface for one minute and then wiping off the excess stain with old rags.
Let the stain set for eight to 10 hours.
Brush polyurethane onto each of the pieces with the paintbrush in a thin and even coat. Let it dry for eight to 10 hours.
Lightly sand the dried gloss by hand with fine sandpaper to dull the surface. Wipe off the dust. Apply a second coat of polyurethane in the same way you did the first. Let it dry for eight to 10 hours, and then reassemble the cabinet.