For me, the absolute safest, and best way to balance a prop is to not remove any material. I use quick drying clear spray polurethane. After you do a few you can pretty much estimate how much to spray on. The light side of the prop will fall, but as the solvents from the clear off-gas it slowly rises to at or near level, where another quick shot gets it just right. It's fast, simple, and above all...safe.

Vince