Place the drop cloth over the floor beneath the work area to minimize messes.
Sand the trim with the sandpaper to prepare the wood for the paint. Rub the sandpaper lightly over every inch of the trim. Wipe the trim with the tack cloth to remove sawdust.
Apply painter’s tape along the perimeter of the trim where it intersects with the wall. Press the edge of the painter’s tape firmly against the wall to prevent paint from seeping beneath the tape as you paint the trim.
Load the paintbrush with the interior primer. Apply the primer along the vertical edge of the trim first where the trim and wall intersect. Keep the primer thin and even to prevent drips from forming along the vertical surface of the trim. Apply the primer to the front of the trim after you finish the vertical edges. Continue working until you prime the entire surface. Allow the primer to dry for at least one hour.
Load the paintbrush with the interior paint and apply it using the same technique you used for the primer. Allow the paint to dry for at least four hours and then apply a second coat.
Remove the painter’s tape after you finish painting.