There are grinder pads available from 3m with a backing plate called the 'sand blaster' and you ought to try those - the work well on the ugly stuff. Do a web search for them as 3m sandblaster grinder pad. They used to have them at lowes. I have also used knotted wire brush on grinder. I did that on my jeep, but the hood was so pitted and stinky that I painted it with zebra stripes so you couldn't see it!
