Adhesion, chip resistance, and metallic control of base coat will increase if 1-2oz. of the activator to be used for the clear is added to the ready-to-spray base. I always do this, and always will, unless the manufacturer specifically warns against it (which I have never seen).
DBC in particular seems to become very brittle when activator is not used in the base coat. In areas where stone chips are a problem, this tendency to become brittle can result in a front end that looks horrible in just a couple of years.