[dsraven]

tempest nailed it. I would use a final paint that is easy to sand or you will ned to let it sit longer to cure up hard. park the truck on an incline, run the garden hose at the uphill end, then wet sand like he advises. with the waterfall effect to keep the sandpaper clean it goes pretty quickly. try to get some dark red oxide as it will look older that way. shoot a good thick layer of the black so if you break through you have a bit of depth to work with or maybe you wanna break through a bit so there is a little black showing here and there.
nice job on the floor