I would start with a drop of hand dishwashing liquid in a half a cup or so of warm water and a toothbrush. Clean a few square inches at a time and wipe it off to see how it looks. After you get the whole machine clean you can use car wax on the black lacquer, going carefully around the decals and just lightly trying a little wax on a test decal on the back to see if it'll take the abrasive in the car wax without shredding.