Sawdust build-up can create heat and friction when you use a hole saw. One solution is to drill a smaller hole inside the area to be cut out that will allow the sawdust to escape. Size the relief hole according to the size of the larger hole. If, for example, you are cutting a 3-in. hole, drill a 1-in. relief hole. Don't drill the hole too close to the center, which you need for the saw's pilot bit.
If you find lumps in a can of paint that you need, you can “push” them out. Cut out a circle from a piece of wire screen slightly smaller than the can’s inside circumference. Put the screen circle on the surface of the paint. With a little help it will sink to the bottom of the can, taking the lumps with it. Another way to salvage lumpy paint is to strain it through an old nylon stocking.