I have a project that I have just started, 88 Mustang GT. I’m planning on using your single stage paint system on top of the contour primer/surfacer. Since this is my first real paint project, I was just curious how to handle all the bumper covers and ground effects on this car. Do I need to add anything like “Flex” to the paint so that it doesn’t crack. Is there anything even called flex any longer . . . Any help would be appreciated.