Normal plugin for GIMP http://registry.gimp.org/node/69 DDS plugin for GIMP http://registry.gimp.org/node/70
Are you using the new car shader? https://docs.studio-397.com/developers-guide/cars/car-art/working-with-new-ibl-pbr-car-shader
No, not using any shaders as far as I know, I am converting a 1994 F1 car from the SR mod. I will have a look though, thanks.
These videos were brilliant in helping me learn: and What you need to do to sort out the 'shinyness' issue is explained in the second