Vent: blew $340 on that creosote powder treatment for a job in Akron

A homeowner on the east side had a stubborn glaze layer and I let the supply counter guy sell me a case of chemical powder treatment instead of just pulling the rotary head out. Followed the label, let it sit overnight, came back and the glaze had barely moved, so I burned two extra trips and a full day of labor. Ended up going back to my whip and chain the next morning and it came off in about 90 minutes like usual. That $340 plus the wasted visits came straight off my own cut on a flat rate job, and I should have trusted the brush. Has anyone found a powder that actually does something on hard glaze, or is it all snake oil?