doopdoop, please share a little more info with us. I see that you are new here, welcome aboard. You should do a search for this topic, it periodically comes up and most of your questions will be answered. That said...
What are you working on, original classic or daily driver?
What are your plans, keeping it forever or driving the snot out of it till the wheels fall off?
What are you painting over? Bare metal, bondo, faded paint, peeling clearcoat?
Keeping the same color or changing it?
How much are you painting? Engine bay, trunk, door jambs, outer body only?
Where will the car be parked when not being driven? Outdoors, garaged, under trees?
Are you looking for a show car, a 20 footer, or something in between?
I did spray Rustoleum on my Duster. But, I also put a clear coat on. It has been about four years now and still looks good - but it is also garaged when not driven. I built it on a shoestring budget. Would I do Rustoleum again - I would depending upon the circumstances.
C