Thanks, Greg. As it happens, I just decided to go for it. It was the bottom of my M1A1 Abrams, anyway. I wanted the bottom to look really scratched up. I had laid down a layer of Tamiya, about 50-50 Chrome Silver/Dark Grey as the base coat. I let that dry overnight, then coated that with a layer of clear satin. After letting that dry a short while, I did a layer of AK Heavy Chipping fluid, then, after about 15 minutes, did a coat of Model Master Acrylic Sand color. within about 10 minutes, I started the chipping. Even with only that short of a time, the sand layer was on there really 'good', that is, hard to get off, but I saturated that layer with a lot of water, and used a toothpick, hard, and those scratches ended up being perfect, at least as far as I had envisioned it. When I had used Tamiya as the top coat, the top layer came off a lot easier, and probably makes for smaller, more subtle scratches, if that's your goal, but the larger chunks that happened with today's experiment were perfect for what I wanted!