Load the brush with paint so it is no more than half-coated. Rub off the excess on the paint tray so it won't drip.
Cut the paint in along the edges using a steady hand and even stroke. Run the edge of the brush close to the corner, allowing the bristles to fan out slightly. Work in 2- to 3-foot sections at a time, reloading the brush when necessary.
Wash out the brush with soap and water, and let it dry thoroughly. These brushes will last for many years depending on how often they are used.
Load the foam edger with paint by dipping it in the paint tray and rubbing off the excess. These edgers are prone to dripping, so it's important to remove excess paint.
Paint along the edge using a steady hand. These edgers are easier to apply a straight line with because of their shape. Work in small sections.
Reapply paint over the previously painted section. Pad edgers tend to put paint on too thinly, so you'll need to go over your work.
Discard the brush. You can wash these brushes, but they're usually quite worn and even falling apart after they're used.