On APC and other similar props, I check the balance as soon as I remove the price tag and sticky stuff with alchohol. On the heavy side, I start by sanding the sharp trailing edge and leading edge off until I get it to balance roughly, then lightly sand the original light side trailing edge just to get the sharpness off the blade. Most of us choke the engine by hand and some props come out pretty sharp on the trailing edge and can cut your finger even when just pulling them through to prime. (Got scars to prove it.) I then finish the balancing by sanding the heavy side leading and trailing edges with 320 or 400 paper.

For smaller props, the best buy going is investing in a Top Flite magnetic balancer. You can balance a bunch of props and spinners with these things and they are only about $20.00. I have balanced up to a 26X10 wooden prop on one of these.

I agree with the light coat of clear something added to the light side of the wooden props. If you apply it very smoothly and evenly, you can actually create a smoother surface than the original. Some have enough clear on them that you can lightly sand them as above if they are not too much out of balance.

If you don't balance the rotating parts, you will pay for it in loss of rpms and excessive vibrations that can easily cost you your airplane. I can't believe anyone would procrastinate in purchasing an inexpensive prop balancer, if they only realized what it will end up costing them in the long run on equipment, running unbalanced.