No one likes throwing away paint. So, after a project it is natural to store any leftover paint in your shed or garage and bring it out when you need it. The problem, however, is that when paint sits in that container for a while, its pigments separate and crusty chunks form. If you don't mix the paint right before starting your project, the final result will look terrible on your wall.
Attach a squirrel mixer to your drill. A squirrel mixer is a mixing attachment available at any home improvement store in the drill section. Place the mixer into the paint. Turn the drill on and mix the paint until all the pigments are combined.
Tape the fiberglass screen over the top of your 5-gallon bucket.
Pour the paint out of its can into the 5-gallon bucket. The screen will filter out all of the dried chunks, making sure that they don't end up on your wall.