Put the metal on one layer.
The basic orange/white parts on another layer
The national markings on another layer
The unit markings on another layer.
These layers don't include the usual panel lines, rivets, screws etc layers.
Once youve done it try it with both material files, see which looks best.
For a good idea on layers work goto
http://www.ah-skins.com and download one of the templates.
For a guide, most of my skins use around 30-40 layers.