RE: Great Planes p-51d
The 2-blade props don't look quite as odd if you spray them black and add some yellow tips. I top-coat them with flat Lusterkote clear. Sometimes I rub some flecks of aluminum colored paint on the leading edge and tips for a more realistic affect. Just be sure to use light even coats so you don't distort the prop shape and check the balance when done. It isn't a perfect solution but it does help a little.