Painting Car Bodies, i.e. - NASCAR or classics

I am starting to do a couple of cars. I have done a couple of airplanes and a couple of Sci-Fi vehicles but I have never done a car. I wanted to start collecting Nacsar Models and there are a couple of Classics I would like to build. Everything I read, shows you how to paint the body (outside) with nice even, equal distance strokes from an airbrush or paint can. A couple of questions though, all instruction or reference mat'l show painting the sides. When and how do you paint the roof and hoods? Are they done first or after the sides and what about over spray? Lastly, what do you do about the inside of the car body? On Nascar, would you paint a primer only then paint the outside of the car the color needed and just leave the inside primer color or what? Please help a new guy oout here. Throw me a big bone to get these projects rolling.

Scott