I quit using sized bushings altogether and use cone shaped "finishing" bushings. I make these myself from urethane rod I just use calipers to turn to size.
Measure the pen hardware that will mate with the blank and once you get close to size by eye take small light cuts with a skew and measure, cut more, measure. It takes a bit longer than just running down to the bushings, but the final results are superior. This is very similar to turning between centers.
Terry