Hutch, you need some type of power buffing wheel. Ideally, if you have a a benchtop grinder, you can mount a stitched buffing wheel on it. Take off one of the standard stone wheels and replace it with a stitched cotton buffing wheel. Home Depot carries Ryobi buffing wheels that will work on a benchtop grinder. Harbor Freight has a line of buffing wheels, too. Both sell adapters to mount them on a drill press or power hand drill.
Then you need some stainless polishing compound. You apply the compound to the wheel and then apply the prop to the buffing wheel (or the wheel to prop).
Because of the shape of the prop, it won't be the easiest thing in the world to polish. Get the biggest buffing wheel you can. And make sure you hold on tight. Buffing wheels can "grab" and throw objects. You might want to practice on a piece of scrap metal to get a feel for the buffing wheel before attempting the prop.
One other alternative: You can polish by hand using some chrome/stainless liquid polish, found at the local automotive store on the wax and rubbing compound shelf. Lots of elbow grease required, and won't polish up as high as a power buffer, but should still be a big improvement.
If the surface rust is tough to remove, you can try hand rubbing it with some #000 or #0000 steel wool and a bit of household machine oil. Don't use steel wool from under the kitchen sink. Too course. Will scratch the finish. The finer steel wool is usually found in the paint department at hardware stores, or sometimes with the sandpaper selection. Walmart carries it.
