I have recently begun work on several WWII era US prop planes and seem to have found a good solution to getting those yellow prop tips painted. Yellow is, to me, the hardest color to apply to plastic or any other material for that matter. It doesn't even cover primer that well. The bottoms of some of these models is white and I have found that Model Master semi-gloss white enamel is the best white paint for models. This paint dries relatively fast and dries smooth and even with no paint dust buildup as with using flat white. Tamiya white acrylic is a close second. Anyway I have started painting the prop tips white before applying the yellow and wow what a difference. I don't have to lay on a thick coat and hope it evens out. The white undercoat really makes the yellow pop. I also have started using the white undercoat for yellow nose and fuselage bands. This may be old news to some of you but I hope this tip has been helpful to less experienced modellers.