Ok here’s what I use bspsource batIn BSPSource go to the last tab and click "Extract embedded files". Go to your tf/custom directory and make a new folder, name it "yourmap_assets (example: pl_metropolis_assets), drop all the extracted files into that folder and restart hammer. If it has been repacked multiple time, its going to get messy and you are going to have to find all the broken textures in hammer and change their file path.
I got the textures out of the folders and I putted it all in oneCheck your map for problems (alt + p) and find the textures that are missing/wrong and fix the directory.