How to Prepare Exterior Wood Trim on Doors to Hold Paint

Fill all nail holes, dents and scratches in the door trim with wood putty using a stiff putty knife. Allow the putty to dry completely, then sand it smooth with the wood surface using 120-grit sandpaper.

Remove wood dust from the surface of the wood with a tack cloth.

Caulk all wood joints using a caulking gun. Run a line of caulk along each joint or crack with the tip of the tube of caulk, then run your finger over the caulk to push it into the crack. Wipe off excess caulk with a damp painter's rag.

Pour 1 quart of primer paint into the paint holder. Dip the tip of the paintbrush in and out of the primer to load the bristles with paint. Apply the primer paint to each surface of door trim in steady, even strokes. Keep applying paint to the brush bristles throughout the priming process to avoid leaving visible brush strokes in the primer coat. Prime over the wood putty and caulked areas until the door trim has been primed. Allow the coat of primer to dry completely.

Inspect the door trim for raised wood-grain fibers. These lift up as the primer dries and cause the surface to feel rough. Lightly sand the door trim using 150-grit sandpaper to smooth the surface without sanding off the primer.

Apply a second coat of primer if you sand back to bare wood. Wait for the second coat to dry. Sand once more, then tack off the primer dust.

Wash out the paintbrush and paint holder. Shake out excess water in the brush and holder.

Pour exterior finish paint into the holder and load the bristles of the brush by repeatedly dipping the brush in and out of the paint. Paint the door trim with long, even strokes, keeping the brush wet with paint to avoid brush marks in the finish. Paint all the trim work as quickly as possible to avoid paint gumming between strokes. Allow this coat to dry, then add a second coat.