Every time you dip a brush into the paint, you must first wipe off the excess paint from the edge of the paint pot before painting. But after only a few strokes of the brush, the edge of the paint pot is full of paint that runs down the outside and inside. So you can't close the paint pot properly when you put the paint away and the paint dries up.

To avoid this spilling, tie a double or thicker rubber band from top to bottom over the paint pot so that the rubber band is stretched centrally over the opening. This way you can easily wipe the brush off the rubber band after dipping it into the paint and the rim of the paint pot stays clean. When you have finished painting, all you have to do is remove and discard the rubber band and stretch a new one next time.