A can of oven cleaner, or engine degreaser, wire brush, and the local car wash is the first step I took. If you have someone with a parts washer then that can do the same thing. Once all the "bulk dirt" is off you can use different types of wire wheels in a hand held drill to clean them up to the finish you want. If you want them to stay clean get some "rattle can" clear coat , and spray a coat or two on them (eastwood company makes a good clear called diamond clear that won't yellow). That way dirt can't stick as easy, and you can hose them off easier
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1970 T1 W/MassIVe 2913cc RAT/?EFI? w/direct fire (very soon) and 915 trans
1962 SC 1776cc SP 944NA brakes, 993 wheels
VKG