If you're looking for a sand-able primer, there's fantastic primers on the market for sanding. But they don't work as well as top end Epoxy primers when it comes to protecting from rust. V Prime DPS3051 is one of the best sanding primers for holdout and gloss retention that I've found. You'll crap yourself when you see the price per gallon, but don't clean that crap off yourself as you'll just be crapping yourself again when you see how fast and easy it sands.