Sewing machine oil (SMO) for all parts black or with decals. Soft cotton cloth to gently dust, then SMO. Remove shiny metal parts, slides, inspection plates, nose plate. A good metal polish will clean these.
You can also use a heavy cotton yarn, like sugar n cream, with a dab of metal polish, wrapped and crossed once around the presser bar and needle bar, pulled left and right, to clean those. Any surface rust can be removed with 0000 steel wool, I like to use steel wool for the handwheel edge.
Your machine is gorgeous, and with a light cleaning and an oiling of the machine and the treadle legs, should sew again easily.