Old sweep in Cincinnati handed me his brush and asked one question about my wrist
He watched me scrub a flue for about 30 seconds, then made me hold the brush loose and spin the rod with my fingertips instead of my whole arm. "Your shoulder is doing all the work and your brush is skipping the corners," he said, and he was right, my elbows stopped aching by the second chimney. Any of you switch to finger spinning on hard flues, or does it only work on soft brick?