Tim,
There used to be an outfit, I believe it was called Spinning Props, what made clear discs to replace props. I'll look to see if I can find the url. In the meantime, here's how to do it:
Using 400 or 600 grit sandpaper gently sand corresponding blured areas from the center to the edge, three for three blades, four for four. If the props had yellow tips, cut a stiff piece of card stock just a little smaller in diameter than the disc, and use it as a mask. Lightly airbrush yellow from the center outwards to the edge of the disc. I didn't have to fill in the nose cone; I've used these discs on a B-17 and P-51. The discs had a hole cut in the center and on the B-17 I just cut the props from the hubs and slipped on the discs.
I'll look for the outfit and get back with you.
Dick McC