These are Paint Shop Pro numbers, but you should try this, Larry.
For NMF Skins:
Specular = Diffuse in Grayscale, Adjust Brightness -15%
Environment = Diffuse in Grayscale, Adjust Brightness -15%, -15% (mathematically this is probably -32% once)
Power = Diffuse in Grayscale, Negative Image, Brightness -15%, -15%, -15% (mathematically this is probably -52% once)
For painted airplanes use -18% for Specular or so, -20% for Environment, and for Power. . . I forget now but try a few things ten percent at a time.
Particularly if you use the Skin Viewer this will give you a good idea what things look like while you're drawing. Obviously you'll have to make final adjustments based on what the game view looks like.
It's worth a shot. Others have had luck with this method. Customize it for your software.