For a driver type resto, I roll on some semi flat black POR-15. Zero Rust may be better because you can get a closer color to the dip gray.

Its a messy job no matter what, but I generally use a wire cup brush on a 4-1/2" grinder followed up with mineral spirits to clean the underbelly.

Go to your hardware store and get a few paint trays for the 2" or so rollers. If you lye on your back and relax, you can roll most of in on quickly. Then fill in the gaps with a brush.