[knomadd]

read the directions first. I believe, even the bare metal primer is suggested to be sprayed in a 72 degree environment. Meaning it won't cure for a LONG time if it's cooler than that. It's never advised to paint in sub 50 degree weather without some sort of heater to warm up the room... or at least a high powered light that generates a lot of heat to warm up the metal. Don't use a heater as it could set the paint on fire.

EDIT: I mean to say, don't put a heater facing the painted part as it could cause a fire. Using a heater to warm up the metal first isn't a bad idea. If you heat up the metal first, you can paint the surface and use a flood light type lamp to help keep it warm to cure correctly.