I work with turbo prop training aircraft, so I see spinning props every working day.
From most angles, all you see is a distorted disc of air, in real life that is. On film/TV
you may well see blurred blades, this is due to the number of frames per second being shown.
So, the easy way to model a spinning prop is as follows;
Get hold of an OLFA circle cutter. This has a pin at one end and an adjustable blade at the other end of an arm, so you can cut different diameters.
Figure out the diameter of your model prop, and cut a circle from clear plastic card.
You now need to fill the holes in the spinner that the blades should fill. Make sure the spinner is smooth & then paint it.
Find the diameter of the spinner, at the point where your 'prop' will sit, and cut or drill/file
a hole in the center of your 'spinning prop'. ideally, if you've done everything to the right size, you'll have a fairly realistic 'spinning prop'.
if you have a minidrill, before you cut the center hole, use a small nut & bolt to chuck the disc onto the drill. TAKE ALL USUAL SAFETY PRECAUTIONS! and at a slow speed switch on. You can now apply wetndry paper lightly to the spinning disc, especially the edge, this will blur things a bit & give an impression of a turning prop. Take care to keep the disc 'see through', a very light sand is all you need.
These 'props' look good on a pylon mounted 'desktop model', certainly better than just
three or four stationary blades.
Good Luck
Pete