I too subscribe to the alcohol method. A lot of solvents such as paint thinner will fog the plastic when it dries, and then its off to scrub it clean with 600 grit sandpaper. Yuck!

I use a large rubbermaid tub, 6 large bottles of the 90% alcohol from the drugstore, and a Black & Decker Scum Buster. Just fill the tub, put the shell in, and let it sit for about 20 minutes. then strip off the silver crap with the SB. Once you've gotten some off, let it soak for a while longer, and repeat. Usually, it takes about 45 minutes to get a shell entirely clean.

Anyway, thats how I do it. I'm sure I'm not far off from most others.
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Electricity tastes good. No, seriously.