When it comes to cleaning metal, I always start with the least abrasive way, such as metal polish or cleaner. But, you can overly rub with these materials and put a high polish on the metal without removing the prints. A very fine sandpaper, for example 1500 to 2000 grit, used with a petroleum based oil, such as WD40, machine oil, etc., might be needed. You need to go very lightly on the affected areas of the medal, wiping off the oil occasionally to check your progress. Steel wool can sometimes yield the desired results. Whatever you use, you must remember the fingerprints are light corrosion, therefore, you are removing small amounts of metal when you remove them. Such a cleaning is likely to remove or "fade" some cross graining. After cleaning. You might notice the areas cleaned are brighter than the surrounding metal. You can usually go back with 1200 or 1500 grit sandpaper and blend the cleaned areas in. It takes some patience and a good eye to do this you might have to lightly go over the entire blade to get a proper look. This should not seriously affect the cross grain, but you have to exercise caution in the etched areas. You want the sandpaper to be flat and rigid, so as not to "dip" into the etching, slightly rounding off the edges of it, creating a "drag" effect on it.