After what seems to be a countless amount of hours poured into body work, block sanding, and prep work, painting could arguably be the most crucial step in the entire process. It shouldn't be written off as easy.
I don't claim to be the greatest painter, but I have learned a lot of very important foundations that make a paint job extraordinary. Here they are:
•Dry Times. Everything needs to 'flash off' long enough, but not too long. Letting the solvent dry out is very important, whether it's sealer or base coat. The sealer should be allowed to dry for just about as long as allowed in the tech sheet. Each coat of base coat should flash off for at least several hours. Always be sure to stay within the time frames listed in the tech sheets so adhesion isn't an issue.
•Sealer. It's important and needed. The base coat needs a solid surface to lay on. Sealer is very non porous and gives a great foundation for the base coat. Always use sealer.
•Base Coat. Above all, every panel needs to match. Whatever the method, all the panels need to be sprayed together (loosely assembled, and spray panel to panel in one pass...'walk the car'), to ensure the color is exactly the same, all the metallic is orientated the same, etc. Even solid colors need to be painted together. It only takes a couple extra hours. Beyond matching, everything needs coverage. Don't be lazy, grab a bright flashlight and check over everything after each coat.
•Clear Coat. Flash times are crucial with clear coat. A good rule of thumb is that the clear coat should be stringy before the next coat. When it is barely still stringy, the next coat needs to be sprayed. (Some brands can be tacked up). This is very very very important. Don't go by the time, go by how the clear is actually drying. If too much time goes by, it is very possible to see the edges of each layer of clear when polishing. This is from each coat not melting together enough because of too long of flash times. Solvent pop can also happen. Don't clear too many parts at once, make absolute sure you can get everything coated in time. Also, don't spray too heavy, good medium coats are perfect. Depending on the clear, usually 5 or 6 coats is perfect to give enough material to sand flat.