Here's a car paint shader I've used in a couple projects that tries to balance accuracy and node complexity. It models pearlescence (flip-flop), metallic flakes, and clearcoat. I've combined it together in a NodeGroup you can use.
Make sure to tweak flake scale based on your object's scale (higher numbers for smaller flakes).
Car body model is from GrabCAD: https://grabcad.com/library/car-body-concept_2-1
It touches the truth