When painting a room which has surfaces that are in good shape, plan on spending about half as much time on preparation and clean-up as the actual painting. Where surfaces are in poor shape, non-painting time will increase accordingly, and may take more time than the paint application itself. To save time in cleaning up paint trays, either line them with aluminum foil before starting, or simply slip smaller trash bags over them.
As a final check when taping drywall joints, use a side light to check for smoothness. The light can be a halogen worklight, a troublelight, a lamp without a shade, even a larger flashlight. Hold the light close to the wall next to the joints in several places to reveal high and low spots, or bumps and depressions, that otherwise would be easily missed.