First: Do you see Bright in the menu File - Export?
Do you get an error message when you use it? If yes, what mis the message?
Using BRIGHT does not mean we brighten the image. BRIGHT is a popular program to convert your image to a 256 color BMP file for IL-2 for example (other formats are also supported).
But we do often adjust the colors for our sim. Since every sim has other effects on the colors.
Actually I often even darken my skins for IL-2. But I do that with a grey layer with some noise on it. This to make the paint look less equal and "glossy". I apply an appropriate Belnding option to that layer and also adjust it's opacity until I am happy with it. (see my Hurricane template for IL-2 in the download section to see what I mean).
At least make sure you have the colors of the pattern on seperate layers. This way you can adjust them seperately. You might want to try a trick like my layer and set the belnding options to lighten and play with it.
I prefer Hue/Saturation over Brightness/Contrast to adjust colors, since you can also influence the tone of the color.