Summarize this article:

Paint with long, horizontal strokes for an even coverage. The thickness of the roller sleeve makes it hard to apply paint around adjacent corners, ceilings, moldings, doors, and windows. Even if you do manage to paint those areas closely, the paint will most likely dry with streaks. Start painting about 6in (15cm) away from the corner of the wall, and about 12in (30cm) up from the bottom of the wall. Then, stop your first stroke 24in (5.110.2cm) from the ceiling. Most of the paint on the loaded roller will transfer onto the wall from this first motion. Leaving areas by the ceiling and corners unpainted will give you the room you need to spread all of the applied paint. For the best paint coverage, mentally divide large walls into sections that are 23 feet (0.610.91m) wide, and divide other smaller areas into thirds. Then work within a single section with 1 load of paint before moving onto the next section with a new load of paint. Aim to cover the areas by the corner, ceiling, and bottom portions of the wall that you intentionally left blank. Use continuous motions that move up and down like a vertical zigzag. Continue this motion until the applied paint is evenly spread for that section of the wall. Always use a gentle pressure while rolling on or spreading the paint. Forceful motions or too much pressure can put streaks in the paint, and cause paint to build-up on the sleeve. If the paint roller begins to stick to the wall and won't spread the paint, do not add pressure. This means the roller needs to be loaded with more paint. To get a smoother coverage, always spread the paint towards the previously painted section. Leave about 6in (15cm) of space between the space you just painted, and the new section. Continue this process until the entire wall is painted. Use the same up and down, zigzag motions you used to spread the paint. You do not have to clean or get a fresh roller cover for this process. The paint residue left on the roller will help blend the wet paint on the wall without oversaturating it. Smoothing out the paint near the ceiling and floor with a vertical stroke is challenging if you have never used a paint roller before. Use a horizontal stroke to smooth the paint near those areas. Examine the painted area during the day, and see if the color pigment is even. Most light colors of paint will require 2 coats to adequately cover a wall. Some of the darker paints may require 3 coats. For oil-based paints, you can apply a second coat after it has dried for 24 hours. Latex paint dries quickly, so you should be able to apply a second coat after 4 hours of drying. Use a roller scraper to remove excess paint from the roller. Run the scraper across the sleeve lengthways. Get as much of the paint off as you can before washing. Then, rinse the sleeve with water until you can squeeze clear water out of it. Allow it to dry overnight before placing it back onto the metal frame. Roller scrapers can be purchased in the painting section at a local hardware store. If you do not have a roller scraper, carefully use a putty knife instead.
Use a paintbrush to outline the perimeter of the wall with paint. Roll the paint onto the wall using a slightly angled, upwards stroke. Spread the paint to unpainted areas by sweeping the roller up and down. Reload the roller with paint and begin painting the next wall section. Connect the separate paint sections with overlapping strokes. Apply a second coat of paint once the first coat has dried if needed. Clean the roller frame and sleeve when you are done painting.