[help request] Textures and paintmods

[Axeface]

Hi!

Im making a new paintmod... mod and I have some questions.

Firstly, I am using GIMP 2 - can anyone advise me about the best dds export options to chose for X4? Im using BC3/DXT5 because thats the one that worked first for me. Is there a better one to use? Should I select any specific options such as mipmaps or alpha options?

Secondly.
Despite spending a stupid amount of time messing with paintmods.xml I still dont understand what the parameters actually do. I just sort of mess with it and test in-game until things look good.
I have done tests but its not clear what the variables are doing because they dont always do what I think they are going to do, and they dont always do the same thing... leading to confusion.

It also seems that if your paintmod is using a texture, the texture obscures ALL variables except 'smooth' (and even that doesnt always make it shiny...) and the red green blue setting? Is this correct? The other variables such as brightness, saturation, hue all only apply to what is UNDER the texture? I have had some dirt show up ontop of my textures, but only sometimes...

It also seems like if you have a texture with dark and bright parts, reflections/shininess only show up on the darker parts of a ship, bright parts are matte/non-reflective (video example).

Could someone clarify what the following variables do exactly and how they interact with any chosen pattern/texture?

strength
brightness
metal
smooth
dirt
extra dirt

Lastly. Is there any way for me to get a normal map to work for my paintmods?

Thanks for any help.