Chuck, you are right...sort of. There is a certain transparency to some colors and that primer color IS going to make a difference even with the "proper" amount of paint. Heck, some colors are so bad that you could put six or ten coats on and it wouldn't cover up black and white checkerboard spray out card used to check coverage.
Red needs lead for good coverage. If this is a lead free paint it may be a little hard covering to HORRIBLE depending brand.
To use a primer color that helps makes sense.
Now, the question I have for 46 in progress is it sounds like you are talking about lacquer primer, if that is the case it is a very bad choice. If you MUST use the lacquer primer, you really need to seal the truck prior to paint. I mean prior as right before, you spray the paint without sanding the primer. So it isn't added work, only a coat or so around the truck prior to paint.
Realistically, unless you have a uniform substrate of cured finish like an acrylic enamal paint that is sanded down to be painted over, or COMPLETELY 2K primed panels you really need a sealer to give you that uniform substrate for your paint. If you have primed the whole thing in lacquer, it will soak up solvents from your paint and you will get a little die back. If you use a good sealer and let it flash off good prior to paint you won't have this problem.
If you are shooting a good old "Geterdone" paint job it is the standard of the industry, enamel sealer and enamel paint over it.
Brian
