Heres how I do it, Darren. It may not be right but it works. Mutiple layer sprayed super thin.
Prep body for paint like normal, if your going to put (rust-throughs) in with a dremal, dents .ect do it.
Then layer thin coats of paint.
Here is my order:
1. Red primer
2. Satin nickel
3. Gloss brown
4. Flat black
5. Gloss red
6. Gloss yellow
7. your finale body color
Let the primer dry completly, then spay 2,3,4,5,6 on about two or three minutes apart so they blend on the body.... light,light,light coats or it's a big mess.
After those dry for a few hours spray your finale color then let it dry completely.
Sand 320 all the way upto 1200 grit then add finishing touches by hand.
I look at reference pictures for paterns, and go slow working from top down.
And be careful not to sand through the primer.
Hope this helps.