Dan,
After measuring the correct prop diameters on the clear piece, I cut the entire circular disk out and placed it on my drill sanding disk. After spinning it on the course sandpaper (just a couple turns because any more, and the clear disk will look more FROSTED than streaked). I'd remove the streaked disk, and cut the prop shapes from that in one piece because it's easier to handle that way. For three or four bladed props, it's easier to keep them all phased properly for the application, but they could be prepared individually if you wanted to.
To replicate the "Thickness" at the base of the prop, you cut the kit supplied propeller blades into short, pointed stubs, sanded thin out toward the point, and attach the clear piece ONTO that stub.... filling and sanding as required to get a uniform transition. Since this area will be solid, the airbrushed black or OD or silver or whatever, will blend the seam so well that it makes it look real... almost magically so!
Hope this helps.... sometimes it's hard for me to explain, I guess that's why I resort to drawing illustrations.
Take care,
Frank