I finally got a brush to stop spinning on a rough clay flue by turning it by hand first
Had a job in an old house near Dayton last month where the flue was so rough my 8 inch brush just kept catching and spinning loose instead of scrubbing. What worked was running the brush down and back up three or four times by hand before I hooked it to the drill, letting the bristles find the grooves first. After that the drill ran smooth and I pulled out maybe a coffee can of soot I would have missed otherwise. Curious if anyone else does a hand pass first on old clay liners, or if you just switch to a smaller brush and take two trips.