Can you spray clear coat over old paint?
Similarly, you may ask, can I spray clear coat over single stage paint?
If you spray clear over that single stage metallic without sanding, in most paint types, you'll get no adhesion with the clear. It may look fine, but the first impact will chip it. Once a paint is dried, the only way to get another paint or clear, to stick to it is to sand it, unless you're dealing with lacquer paint.
Furthermore, do you need to clear coat spray paint?
Clearcoat spray paint is a good solution for projects that need to be sealed as a final step to preserve their finish, color, or surface. It comes in so many formulations that you should be able to find the perfect one for your project easily.
If you are spraying clear over old paint, or redoing damaged clear coat on a project, the prep is the same as for any other paint: Wet sand smooth, feathering the edges of any old clear coat. Clean with a finish cleaner/de-greaser like PRE paint prep. Then, wipe with a tack cloth to remove any dust.