Up until now, I've used dxtbmp to resize/export textures from 2048x2048 to 1024x1024, and whilst the quality is not as good (obviously), it has worked ok-ish. However, that method does not really work for USAF C-17 paints-in particular the band on the tail, where the band colour bleeds through its border when saved as a 1024x1024 bmp or dds (the 2048x2048 dds textures are completely fine, as are the 1024x1024 pngs I have for each repaint). This is the case on my WIP paints for the 155th AS, and indeed Graham King's original repaints for most of the other squadrons.

Does anyone have an alternative/superior method for creating 1024x1024 textures from a 2048x2048 original? It may be easier with photoshop or paint shop pro but I'm stuck with GIMP for now.

What I use is one of two methods.
For the manual approach try using Paint that comes with Windows. I make sure that the original 2048 texture is saved as a 32 bit bmp first. Then load it into Paint and resize to 50% and save as a 24 bit bmp.

When you reload into DxtBmp you just add the alpha saved from a scheme that you have for your sim, this makes the 24bit a 32bit scheme. You can then save it as that and also as a DXT3 or DXT5 according to your needs.

The other method is to use Texture Manager from Don Grovestine. It can make several steps at the same time.

Try both methods and see which one suits you best.

Thanks Steve, I will try out both methods and see what works best.