Erik:

Most of the time it is not all that important to balance the 9 or 10" props on a trainer plane. If you wish, you can buy the Du-Bro or whichever prop balancer rig at about $20.00 When you move up to the larger 12 to 24" size, then it is best to balance. To balance horizontally, you can paint the light tip till it hangs level. To balance vertically, you have to sand or file the heavy side of the hub till it is as close to vertical as possible. Personally, if I trade for a larger glow or gas motor with a Master Airscrew prop on it, I'll take it off and use it for stirring paint. All my 46 to 60 motors have APC props and the large gas G38 to 62's have T/F PowerPoints.