Call me different, but I've decided over the years not to use a primer on my auto models (unless it's a red or black plastic, but for sure not on white or light grey). I figure the less paint on the model, the better from a scale point of view. I also cut all my lacquer and enamel-based paints (including Testors Boyds) with lacquer thinner - it tends to cut down on the drying time and reduces the tendency for orange peel. Whatever you decide to do, the absolute key to a great gloss finish is a finishing kit such as Micromesh's. You'll wet sand the final paint coat with progressively higher number grits of sandpaper (from 2000 to 12,000), then finish it by polishing the surface using a carnuba-based paste wax. Works like a charm. Incidentally, here's that Boyd's True Blue Pearl paint on a '69 Vette with no primer and polished out with a micromesh kit and modeler's wax:
