What? You think source is easier than Goldsrc? I think the opposite!
There's a few rules you need to follow, such as ensuring your texture dimension are powers of two, and that your image is (finally saved) as an 8bit BMP file.
If you're using Photoshop this is crazy easy, just make a texture as normal and then change the image mode to indexed colour once finished, and Photoshop will do it's best to find out the best palette that keeps the image as close to the original as possible. Drag and drop your final image into Wally, save as a wad, it's literally that easy.
Wads are completely self contained, so once your images are in the wad file, that is the only thing you need to keep in your folder. You don't need to keep the individual images around like with vtfs