My guess is that many of you "old salts" (myself included in the old catagory) have your own way of balancing props. Lets hear some suggestions for each type, wood, composit etc. Which side to sand, if that is your method, paint tips, etc.

Normally:

I try to do the ballancing in the sanding off of the mold flashing (and sharp LE... TE can stay sharp because of how I hand-start) of the nylon/composite (Master Airscrew black, APC grey, Bolly Clubman) props. I rarely paint the tips of these.

I will first lightly sand the wood props on the front to get them close to proper balance, then I will dope the light lade face one coat, then coat the whole prop and re-balance. (repeat as needed) If I'm painting the tips for scale effect or increased visibility, I'll do it just before the clear coat. (sometimes double coating the light blade with the color.)

I always avoid alterign the rear of the blade, as changing that side slightly can create a dynamic imballance. (changes the AOA of the blade)

I use a small piece of aluminum duct tape placed near the tip on the rear face. It does not lift when exposed to fuel and I've had some on for years. The front surface of the prop (like the upper surface of a wing) is the most critical, and the very thin tape on the rear surface presents no problem.

What a great topic! Wish I had a great answer, but I don't. What ever works, works, keeping in mind a few things. A prop is nothing less than an airfoil and any alterations to the geometry or weight of one blade or the other will change the effects, for better or worse. With that said, a prop must be in balance, thus the dilemma of how to do it. In my years of modeling, I've not discovered the perfect way to balance a prop. Anything I've been told or tried myself has always been a compromise to the geometry of the blades. You may get the prop balanced by sanding this or that, only to have changed the tone of the prop, where one side is pulling harder than the other. This can cause a different vibration all together. I like the balancing by paint or finish technique that Fred has described. This seems to me to be a method where one would at least keep to a minimum, blade distortion. This is an area where the manufactures could really make some improvements. I've bought props that were so out of balance that they were unusable, primarily in the wood prop department. Yes, a major manufacturer made them. More times than not, it is because the hole was not drilled to center. Wouldn't it be great if a manufacturer marketed props that were guaranteed to be in balance? I'd pay a few extra bucks. Happy Flying!