I was told by a gentleman that has sold Featherweights for about 40 years to use a carnauba wax paste. Just don't rub too hard around the gold detailing. I used it and it worked fine.
Another sewing machine repair person was working on another one of my Featherweights and there was a rough spot on the bed of the machine. It looked like someone in the past had put some masking tape on the machine and the residue left had hardened. He took some regular oil, that you oil your machine with, and used it to get rid of the spot. I was really impressed when it all came off, because I had tried to remove it myself with a mild soap and water and it hadn't worked.