Study this jpeg of a P-47D-40 fuselage side. See how he blends different colors of greys and blues. This is what I used as an example for my "Bonnie" P-47D-11, but I went with lighter shades. I think Waffle originally made this image; and I was so impressed with it I saved it.
Grab the jpeg and paste it into a P-47 skin bmp and take a look at it in game - play with it, make changes and see how that affects the look in the game. Persistance and experimentation will pay off.
Nopoop also made a nifty .psd file of a section of his P-47 - he can email it to you, or with his permission I can email you the one he sent me. He has another technique for simulating bare aluminum shine that's really cool.
Also, go to AH Custom Skins and download Octavius's bare metal P-40 skin and study that one's bmp files. It's and awesome skin.
Keep at it!