I replied to a post similar to this a few years ago. I'll give you the abbreviated version on how I did it. I painted the props (yellow tips in my case), then scanned them into PhotoShop. Using the "radial blur" (spin) function in the "Filter" drop-down menu you can create the spinning prop effect. Once I got the effect I wanted I printed the images on adhesive clear label stock and then mounted them on clear plastic cut to the proper size. As I said at the time, it's more art than science. I tried making decals, but the plastic label stock produced better results. Check the December, 2014 Online Reader Gallery (B-17G "Tailwind") for an image of the model.