Wash the trim with a mixture of water and liquid detergent. Scrub dirt buildup with a sponge. Wipe the trim clean with a damp cloth.
Sand any spots of glossy paint with 220-grit sandpaper. Dull and smooth the glossy surface to accept the new paint.
Place painter's tape around the trim to be painted to protect the rest of the exterior.
Paint the outdoor trim with trim paint and a clean brush. Start at the top inside corner and paint down the side. Paint the opposite side and finally the top and bottom.
Paint the outside edge of the outdoor trim with a clean trim brush and trim paint.