check this link
http://www.rcuniverse.com/forum/m_25...tm.htm#2584856

Here's what I do....
APC Props
1 Leave the edges sharp....I like my finger carrots sliced evenly
2 Put prop in balancer....heavy side will drop.
3 Spray bomb paint the lighter tip with red paint......makes it a bit more visible and gives a realistic effect when chopping your fingers
4 You may want to balance your spinner also...there is a thread here that tells you exactly how to do it.

Wooden Props
1 Will still do a number on your fingers...not as good as APC
2 Put prop on balancer....heavy side will drop
3 Spray bomb varnish on lighter side...let dry and rebalance until the prop is balanced.
4 You can also use a mixture of 5 min epoxy thinned down with rubbing alcohol and paint this onto the light side with a brush.
5 You can also use white paint on the lighter side until balanced.

One thing to remember though...some guys may differ here......
Apply paint, varnish or epoxy thinly to the front of the prop blade near the tip.... It changes the shape to the back of the blade slightly and since the blade is an airfoil basically, it will swirl the prop wash/disturbance over the wings and stab. Hmmmm...dunno if I got that out correct.
Again...some guys prefer to sand the heavy part of the prop blade when balancing. To me..that weakens the prop.
It's your choice basically.....what ever turns your crank... er...prop?
Cheers.