I used the powder and wax plugg once at my "beginnings", to form 220R to PPC. I did not like the result at all.
I has that feeling of waisting my time at the range. It is time consuming, that is no training.
Then I had to spend a hell of a time to clean the wax build up from the barrel.
Then I did not like the headspace distribution. It was not concistent, and my guess is that either the play of the rim inside the extractor claw or the progressive wax build-up bring some variation.
For a long time now, I fire form with a bullet seated very hard in the lands, pushed back at bolt closure, high neck tension and regular powder for the caliber/bullet weight mix. There is always a load strong enough to get good forming and that works correct enough so I can "shoot for real" at the bench while forming. OK it's not shooting in the 1's, but it's good enough to show you that you did or did not not pay enough attention to ... something. It is training for real.
I have found headspace to be much more consistent that way.