Hi!
First of all, the texture flags tab is for fine tunning, it usually remains untouched. You should rather extract the textures from the original livery using the “Extract textures” button on the right. You’ll be prompted to choose the aircraft model (GLTF file) and it should extract the textures for you under the “textures” folder of your project.
I’ve promised earlier to make such a video, but have not done it yet. I was preparing an improvement before filming it, but halted development do dedicate to other projects (actually, I didn’t have much time for MSFS then). I’ll try to make a video tutorial soon.