The last one I did (which was also my first in a long time) was to brush paint the outside Testors steel. This came out much lighter than I wanted, so I applied a "wash" using the top layer of unstirred Testor's acrylic flat black - it ends up with a lot more pigment and thickness than a standard wash, and did a decent job of darkening the whole thing and accentuating detail. The color still isn't quite right, but I'm happy with it.
You'll note that the insides (at least on an F-15) appear to be off white and dark (black with some brownish tints on the borders with the light areas). To try to replicate this, I painted the interior black, and then used my airbrush to paint white lines inside (varying success; use the finest line you can).
I think a lot of your ability to replicate this inner area depends on what you start with; I used the kit's parts which had no detail inside (part of the reason for varying success). Other manufacturers and aftermarket parts may come with more detail molded in, which will assist you greatly if you're shooting for accuracy.