There is a difference between static and dynamic balance. Dynamic blance is very important for EDFS because of the huge RPM range (ie some turn ~50K RPM or more) as compared with most prop planes (~10K to 20K).

A good place to start is to statically balance just the rotor on a precision balancer. Be very careful the rotating parts of the balancer itself don't skew your results. Small rotors will appear to lose balance simply cause you turned the shaft or cones even on the magnetic balancers.

What I do for static balancing of a small rotor is to use the magnets that came with the top flite balancer, put them in a vise, and then use a drill bit of the correct diameter as the shaft. Space the vise with the magnets on either jaw so the point of the drill bit touches one magnet and the other floats (with the rotor on the bit). If you get the jaws too close, the bit will jump to the other side. You can do this without a vise, using something else to hold the magnets, but the screw action adjust is nice if you have a big enough vise.

Static balance alone often isn't good enough for a smooth running fan. A lot of advice will boil down to trial and error combinations in re positioning the rotor in small increments when installing the rotor/fan assembly to get any small runouts of the rotor mount (ie collet assembly and motor shaft itself) and imperfections of balance for the rotating parts of the motor to "play together" at certain speeds. The discriminator is the amount of VIBRATION you feel (or don't feel) with each combination. With small fans, people often hold the fan in their hands to feel this vibration, but I don't recommend that approach for safety reasons. It's better to make a test stand with a soft mount from a U shaped piece of plywood or similar and gage the vibration by the sound and feel without using your hand to hold it. Guys who have actual equipment and precision fans will add weight to the inside of the fan near one of the blade supports in the form of clay, or glue or tape until they get a smooth run.

Do some searches on RC Groups. You'll see it's a topic most choose to avoid, so having the pre-balanced fans (dynamic) from wemotec, HET or the larger names is a big plus. Still knowing what is going on will help you maintain a smooth running fan.

Joe