It's a tad expensive, but in the long run it will save time: You can buy a drill bit with the tip smaller than the rest of it and just the right size to fit in the original prop hole. Then use that in a drill press. Clamp the prop in a drill press vise. I got mine from B&B Specialties, which advertises in "High Flight" and I think in other modeling magazines, too. Of course, you may need more than one, though I just have one in the right size for my larger engines.