Remove the cabinet door from the cabinet by unscrewing the hinges. Completely remove the hinges and knobs, and set them aside.
Wash all areas that you want to paint with surface cleaner and paper towels.
Apply masking tape around the edges of the cabinet to protect the bathroom wall from getting painted.
Spread a tarp on the bathroom counter and floor under the cabinet to catch any dripped paint.
Fill in any holes or dents with wood filler, scraping it flush with the surface using a putty knife. Allow the filler to dry for the time recommended on the container.
Sand the cabinet and door surfaces with 80-grit sandpaper by hand or using an electric sander.
Wipe the surfaces with a tack cloth to remove any sanding dust.
Apply a coat of primer to the surfaces using a paint brush or roller.
Allow the primer to dry, then lightly sand it with 220-grit sandpaper before applying a second coat. Allow this coat to dry as well.
Sand the finished primer with 220-grit sandpaper, then wipe it with a tack cloth.
Paint the surfaces in two coats of semi-gloss latex paint in the color of your choice. Allow the first coat to dry completely before applying the second.
Reattach the hinges, knobs and door once the paint has dried.