To ensure you get a lifetime of use out of your synthetic paintbrushes, clean each one immediately after using it, before the paint has a chance to dry. Wipe the brush on newspaper to remove excess paint. Then stick the brush into a bucket of warm water and move it around to remove as much paint as possible.
Next, hold the brush under running water. Run a wire brush (or a kitchen fork) down the bristles to remove dried paint. When the water running off the bristles turns clear, the brush is clean.
Let each paintbrush air dry, then wrap it with the cardboard cover it came in or heavy paper (like grocery bag paper). To keep the bristles straight, hang the brushes from a nail or hook, or store them flat.
If you do a lot of roll-on painting and use premium roller covers that you don't want to throw away, get a Roller Washer ($15). You'll be glad you did. It's easy to use and gets the rollers incredibly clean—a task that takes a long time by hand, and even then you rarely get a truly clean nap. Just hook up the hose to a faucet, slide the roller cover into the tube, and watch the water flush out the paint in minutes. Order the Roller Washer online by typing “roller cover washer”into your search window.