Takes a piece of equipment that costs upwards to $20k....the most popular is the heins, which is about $8k...if you could find a working quillen, that would run you about $2k-$3k....but they are no longer made and you cannot get service for them....
And before ANYONE comes on here and tells you can do it with a prop balancer, the niftech unit....or better yet, a pair of razor blades....they are WRONG. You can't balance a motor correctly that way....and while it will get the motor in the ballpark, it will still be off enough to effect motor performance...
Later EddieO