Wood is difficult to paint because it isn't a solid color. Look at any piece of wood and you'll see a lot of grain in it that is a different shade from the main color. I've seen a lot of wooden props painted that I would swear were carved from wood, but I don't know exactly how they did it.
Two piece of advice:
1) Experiment on some scrap styrene. Paint it the base color and then take a very fine brush and paint some lighter streaks down the length. Use a couple of different shades of lighter colors and play with them until you find something you like. You might also try a brush with very short stiff bristles and "Dry Brush" some streaks down the main color. To do that just barely touch the brush to the paint and then wipe most of it off on a paper towel so that there is barely any left on the brush.
2) Post this on the aircraft forum and see if they have any advice. This is where it should be since it's oriented toward painting, but you'll probably find more people who have actually done this in the aircraft forum. I know I've seen some photos of WWI models with wood props that looked beautiful.