Well, you don't have to worry about it rusting. Some people can do pretty good repairs with an aerosol can, one of the tricks is spraying through a mask (a piece of thin cardboard with a hole in...
If that's a plastic wheel arch--to me it looks like the black spots are the plastic, which means polishing more is only going to make it worse, not better. IMO Dr. Colorchip isn't going to help you...
I'm not going to dignify that rant with a response, other than to say I don't "always hate on Darren". I didn't even remember the guy's name, and I don't believe I have ever said anything about him...
C'mon man, toothpaste may have sodium fluoride in it, but that's not hydrofluoric acid. Did you know that water has two hydrogen atoms in each molecule? Do you know how flammable hydrogen is?? ...
You could try doing a spray can clear touchup on it...it likely would look the same after, I don't know. 1K clear touchup will yellow over time though.
Ok, number one, it's certainly possible to go through the clear by hand. You were using a fairly aggressive pad with a fairly aggressive compound, and by your own admission, "got to scrubbing". ...