Hot take: brushing with the same poly brush on every flue is why I was leaving creosote behind
I ran a poly brush down a clay flue in Providence for 6 months before a homeowner showed me a mirror shot with a 1/4 inch band of glazed creosote still stuck above the smoke shelf. Turns out hard poly just rides over that shiny stuff and a metal brush followed by a rotary whip on a drill gets it off clean. How many of you are still using one brush for every liner out there?