I'm in the process of cleaning up my Dommie engine casings for my project. I started out by degreasing and getting all the muck off, then onto paint stripper and wire brushes (drill mounted type). That took care of the laquer and trhe inner casings are staying as buff ali. Andy230 suggested wirewooling with old engine oil to give them an age related patina, but I haven't tried that yet.
As for the outer casings, it's been a case of sanding down with ever fine paper, then wet'n'dry to get the marks out. After that a set of felt polishing mops stuck on the drill followed by autosol and elbow grease. No plans to re-laquer them, rather spray with ACF50 (have I got that name right??). This is a toy project bike so won't see much winter muck (the rate I'm going it wont see any kind of road muck
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