@wildbill23c , a couple thoughts, certainly not challenging, but I’ve done the Rick-stoleum paint job many times. & a little of the Chem Engineer here.
Car paint and clear coat are two part paints like an epoxy. The light solvent in the paint (I.e., acetone) is a vehicle to carry and distribute the paint, not actually part of the paint, and it flashes off very quickly. Then the two part paint spreads out and chemically reacts to hardness. Completely different than Rustoleum.
Rustoleum actually has a fish oil base, I’m sure they’ve synthesized that now, but that oil is actually part of the paint. When you thin it down to spray it, you also compromise the integrity of the paint. The oil holds the pigments, and that oil solidifies in the drying process. It actually chemically cures like a varnish or tree sap, not just dries. It’s thicker, so it has a long time to level out. If you use some thinner, that is exactly what it does, thin it. The thinner also flashes off but much more slowly. If you use rustoleum like a two-part auto paint, might be the worst of both.
First thought is the clearcoat. The rattle can clearcoat or the professional two-part clearcoat is not going to adhere properly to the oil-based rustoleum, and it will probably start to flake in a year or two at most. It’ll look great when you do it, but it will fail. The rustoleum provides a very thick coat, so you can sand and buff it, and if you bring out the warmth before the paint is totally cured, usually in about 5-15 days, you can put a very smooth high gloss on it. By itself it’s extremely durable. An extra coat will be far superior and durable than color and then clear coat.
if you’re going to spray the Rustoleum, yes, cut 50% or it won’t SPRAY well. I emphasize “spray” because the thinner is going to help you move it, but it may actually hurt it once it’s on the truck.
The role and tip method (Google it) lets you (1) get a very even coverage from the roller, and then (2) the tipping with a brush smoothes it out, and then (3) it’s thick like honey, so then it will level out amazingly smooth all by itself.
If you do the role and tip, or even if you just apply it with a paintbrush which I’ve also done, you only cut it about 20-25% max. Long dry time. Several coats, when very dry to the touch, but within 48 hours of each other. That way it becomes one thick coat, not thin layers. Sand drips and rash in between, and after a week, you can wet sand and high speed buff it, but I’ve never gone that far, they’ve always looked great after two or three coats.
In a couple months, you can polish it and wax it like any other paint, and I firmly believe it would last twice as long.
And, BTW, I’m not that smart. In my engineering/construction career, I learned all this from the horses mouth at the rustoleum company. I’m just great at plagiarizing!
and one last thought. If you followed me at all, I’m damn arrogant and proud that I’m going to have a $20 paint job and the truck is going to look great. I know from past experiments, everybody will love it, and they think I’m smart because I did a good job with no money. What I have never done, is try to do something very cheap, but then pass it off as if I had it done in some high-end body shop. People can see right through that. So my recommendation is paint it with a roller & brush, and own it, and be proud of it!
I did hesitate before posting this, but I know this site is all about helping other folks, and it is intended in that vein. Nobody should screw something up because they didn’t learn from all of my many many bad screwups along the way!!!