3 blade props are "usually" used when you need more ground clearance for the prop. When going from a 2 blade to a 3 blade prop as a rule of thumb, you drop 1" in diameter.

There are several different balancers available. The simplest is the hand held one. It is an arbor, machined to points on both ends and has 2 cones that screw onto the arbor that center the prop and hold it in place. You just hold it between your thumb and finger lightly. The heavy blade will swing to the bottom. remove a little material from the heavy blade or add paint to the light blade until the prop no longer swings. It's easy to do and only takes a few minutes.

I keep one the hand balancers in my flight box, but also have a base mounted unit the has magnets to support the arbor for a more free motion. Either will get the job done satisfactorily. The base mounted units are a little more accurate.

Rod