Well, it's really a special, secret formula/technique that I've come up with and I probably shouldn't share it... ah heck, why not.
I used dishwashing soap, mixed with warm water, and some 0000 steel wool. Now before everyone freaks out and says NOOOOOO... don't use steel wool on your drums or anything metal, you have to use a very light touch. Basically, the weight of your hand is more than enough. And use 0000 steel wool, 000 or 00 IS to abrasive.
Yes, steel wool is abrasive, but so is just about ANY metal polish. How else can you remove rust, pits, etc... without taking some of the surface off.
I dipped a chunk of steel wool into the soapy warm water, and then with a VERY gentle touch, went over a small section of shell. Next, wipe that down with a wet cloth (clean water, no soap) and then dry with a soft, dry cloth.
That's it - No polish used and it took about 15 to 20 minutes to do the entire shell. Lugs got the same treatment and I even did one lug with my usual metal polish, just to compare. Guess what??? The soapy steel wool lug looked better and was NOT scratched up in any way.
Obviously, a heavily pitted shell wouldn't come out looking like this one did, so I was lucky that 99.9% of what made the drum look like crap was years and years of fingerprints and other crud buildup.
So, if you use this technique, remember the rules...
Use plenty of soap in your mixture. It helps remove greasy crud and also cuts down on how abrasive the 0000 steel wool is. Go slow, do a little at a time and don't apply more than the lightest pressure.
Last rule... if you screw up, I'm not to blame :)