Match the size of the pan to to your stovetop heating element; more heat will get to the pan and less will be lost to the surrounding air. A 6-inch pan on an 8-inch burner will waste over 40% of the energy used.
Using a power drill and paddle attachment mechanizes the job of stirring paint, but it can cause splatters. One way to solve the problem is to use a paper plate. Punch a hole in the center of the plate and push the end of the paddle attachment through the hole before chucking it into your drill. Then hold the plate down over the open can while stirring.