I like spraying normal clear or single stage urethane with a matting agent added in so you can get the exact look you want. More flattener= duller finish.
We just painted the firewall on a '70 El Camino with single stage urethane, flattened with PPG One Choice flattening agent. We mixed three parts paint (just paint, no hardener or thinner) to one part flattener, or 33.3%. Then added the right amount of hardener/reducer.
It looked like this:
I also painted a set of headlight rings for a '55 International pickup recently using the same urethane single stage with 25% flattener.
The inside of these doors were painted with PPG 2021 clear with flattener mixed 1:1.
And a Jeep I painted with 2021 clear and flattnener, also mixed 1:1.
