I couldn't find a picture of one that wasn't anodized, but if this one is NOT anodized, you could use something as simple as some Mothers or Never-dull. Just rub one of those on the amp, if the rag turns black, it's not anodized.
However, most amps are anodized. Even the ones that appear to be bare aluminum are usually clear anodized to prevent corrosion. I'm sure there are some out there that aren't. I'd bet the old RF black/grind amps were bare because the portion that appears bare is usually pretty nasty looking.
If it is anodized, the only DIY ways I know of to get the anodized layer off are to sand it down or strip it with oven cleaner. I've used oven cleaner on some paintball guns and it works pretty good, but it kinda stains the metal. The stains buff out pretty easily with a buffing wheel and some emery compound, but I wouldn't want to try to do it by hand.
The amount of trouble you have to go through is directly proportional to how shiny you want it. If you want it perfectly flat and like a mirror, you'll have to sand out the milling marks. If you just want it shiny you don't have to go that far. There's a good tutorial http://www.caswellplating.com/buffs/buffman.htm that will tell you all about the different types of compounds and wheels if you want to give it a serious shine.