Spray can and clear coat question

Maybe if all goes well this summer, I might be able to repaint the engine bay and trunk of the 68 Barracuda. I've done it before with paint from spray cans and it worked okay. While looking at rattle cans on line, I noticed each offers clear coat as well. At what point would one apply clear coat over top of paint? When it is still wet, mostly dry, or wait until it is completely dry. Thanks for the help you all have given me.