[pinit6]

I happened across that Cleve vid on balancing too - it only made sense that at the scale speeds these things travel, any elimination of vibration would have to be a positive.

Had a small machinists vice I had made decades ago & it filled the bill nicely while also being .. you guessed it ; a vice.  Useful for holding things. 

     

On most any / all of the solid axles there is a tiny nub left from the parting off process in manufacturing, it's but just a few thousandths ( if done correctly ) but thats all thats needed to have it spin perfectly on center.  

   

It really is apparent just how unbalanced a wheel is with even a shortened, hollow grub screw in place. 
Have only used it once too, but balanced 4 wheel sets.      
Like others I haven't really experienced lowered times I can quantify, but the car is just a bit quieter on track satisfying to a degree an obsessive nature of leaving no stone unturned.