Extract the game files, use QuickBMS with the .gfpak script to unpack and repack the textures, then Bntx Injector to export the textures as DDS files to be edited in Photoshop and then use it to reinject them back.
QuickBMS was basically the way to extract files from the gfpaks and back into gfpaks after editing.
It didn't work 100% of the time, the files that you got from it were named something like "0000000DA1"
But in other words it was the way to do this stuff before STB got SwSh support.
Yeah the QuickBMS method worked horribly but at that point in time, it was the only way.
And hey, thanks to it I managed to make a simple texture hack 4 days before SwSh got even released(officially)