If you buy your paint in summer or fall, you can often save some money, but this means youll need to mix it well prior to painting. In fact most of the paint in the store has settled long enough to have separated, leaving a thin solvent-rich layer on the top and 2/3 of the paint as a sludge on the bottom. Intended for less stubborn house paint, ordinary mixers clog up with the goo, taking 15 minutes or more to properly rejuvenate a can. After a dozen layers of paint build up, they scarcely mix at all.
The solution is something larger and more open. Five-gallon mixers move more liquid at the relatively low RPMs typical of a cordless drill. They better clean the bottom of the can and they dont clog. You can improve them for bottom paint by gently bending the blades on the bottom and sides to a slightly greater angle. Even better is the simple laboratory axial flow impeller. These dont clog and will mix the most stubborn can in two minutes.