I use Rustoleum rusty metal primer and Rustoleum gloss black in a rattle can.
That paint flows real nice and self levels. Touch ups for boot scratches blend right in.
Ace hardware will never run out of it.
It's good enough for my '49 to take first place in every judged show on the east coast of Virginia.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission