That XP-47 looks awesome Milton!
Some brilliant textures on that thing.
Willy,
To understand layers, imagine this. (Very simple). In the old days, Disney would put layers of things in his cartoons when assembling scenes. Note that when he made these scenes, the end result was a camera looking 'down' on the stack of layers of a scene. He had the background (base texture) and then the actors being animated (stripes) then he had foreground objects like bushes and trees that were the 'top' end layers, (this in a plane layer texture would be shading, mud, highlights, divets, etc that would be on 'top' of the paint colors).
So.. On the bottom bottom (on a plane's layers stack), you would have your template you will paint on. Then your base colors. Then your stripes and insignia and things. Then above them are rivets, shadings, etc.. Each one, its own layer... Labeled and strategically placed..
You keep that master file 'layered' and never (never) collapse the stack to one layer. Always keep it expanded. Then when you need a Bitmap burned off of it, click 'Save As' and select Bitmap. You keep your Layers version as well. Imagine a layer stack as like a Gmax file, and a Bitmap as the MDL (model) file.
You can also make Alpha channels easily from 'doctored' Layer files, but rename it before you turn it into a Alpha channel master file. (I call layers PSD files 'Master' files).
I hope that helps in realizing how layers work. It bewildered me for the longest time. I would keep remaking them from scratch and was constantly collapsing the stacks. Bad move. Keeping the layers seperated allows you to 'tune' brightness and opacities of say rivets or panel lines on different colors of paint schemes. For instance, you need less 3D effect on rivets on a black paint scheme, but very 'moderate' 3D treatment and shading on rivets on a white paint scheme or they go transparent against a bright background. So with layers, you are afforded the ability to tune each layer with opacity, brightness, etc, etc..
Bill