I'd recommend the orbital or jiggle types rather than a wheel buffer. They are less likely to dig into the surface. If you are going to use a rotary one attached to a hand drill, set your drill to relatively slow speed. You are not polishing a hard surface, you are smoothing a soft substance.
When I lived in the SouthWest (Nevada, Arizona, etc) I always let the car sit in the sun for a few hours before applying the paste wax. Metal surface at 120 to 130F smooths out the paste wax REAL quick.