This application is small enough that the best answer depends on what equipment is most readily available.  The container can be a drum, either plastic or metal.  The mixer can be a 1/4 hp direct drive-portable mixer with a propeller or hydrofoil impeller.  The mixer needs to be mounted off-center at an angle to prevent uncontrolled swirling motion.  The ideal situation is a flow pattern that goes down from the mixer impeller, across the bottom of the tank, and up the opposite side, with as little rotational motion as possible.  The axial discharge from the impeller can be used to create flow in the opposite direction of the natural rotational flow created by the rotating impeller.