To prevent dirt, dead bugs, and paint lumps from ruining your next painting job, try this trick: Cut a circular piece of aluminum window screen slightly smaller than the inside diameter of the paint can. Press the screen disk down into the paint. As it sinks, it will trap any debris and carry it to the bottom of the can.
When you’re finished painting, fish out the screen with a piece of bent wire and rinse it clean for reuse another day.