Start with washing it and see how much comes off. Then nevr-dul will shine up good surfaces satisfactorily.

There are likely hundreds of ways to clean it up. Use the simpler products first. Soap and water. Car wash soap should work. An orange degreaser for what that doesn't cut.

the nevr-dul is a wool wadding with petroleum distillate in it. A very light kerosene, or the sort. Cleans well, and doesn't scratch that I've ever seen.

soft brush-old toothbrush perhaps to get in tight spots. Looks like typica barn grunge or oil
film. Maybe it was sprayed with something to preserve the finish, like fluid film. You may have a real gem under it.