I bought the Durablock kit and used it through my entire build. Basically, start with a long block and sand in long strokes past the damaged area. Spray more high build 2k, then mist it with dark primer. Sand again. Any dark areas means a low spot. Spray more 2k, mist with dark primer, sand again. Repeat until you no longer get low spots. Each step I would work up to finer sand paper grades. Usually, 220 for roughing, then 320, then 400.
