Propeller paint job

Do you mean the spinner or the blades themselves?

If the spinner...those can be a pain! I've had some luck shoving it into one of those plastic circle templates and using that as the mask, but you usually have to go back and do some minor cleanup.

 Thanks for the quick response Doogs; to be more specific I should have said the spinner portion, not the blades themselves. My first try was not even close to being symmetrical; i had to take measurements from a reference point 90 degrees apart around the circumference and it still looked a little off. It's enough to drive the perfectionist in me crazy!

The way I go about: Wrap the spinner up in tape, put the base of the spinner flat on you bench. I place my exacto knife flat on the bench as well, usually need some spacers to adjust the height of the blade, make sure your blade is parrallel to the bench. Put the spinner to the blade and turn the spinner around, keeping the base firmly on the bench.

Use Ambroid or Micro Scale Liquid Masking compound.

Thanks for the tip. That's exactly what I did and it worked. I used a block of wood with a groove cut in it to accommodate the knife longitudinally  and shimmed to the correct level. The paint job is as close to perfect as I can hope.