Update: I stopped sweeping through the fireplace and it cut my soot load in half
I used to run my brush straight up from the firebox until a guy named Dale in Kalamazoo pointed out I was just pushing creosote back down onto the smoke shelf every single time. Went through the damper first on a 1940s brick ranch last month and pulled out 3 times the junk with half the mess, so now I want to know how many of you are still going in through the fireplace.
Man, I feel this in my bones because I spent years doing the exact same thing and wondering why my chimney never seemed to get any cleaner. Going through the damper just makes sense once you think about it, since gravity is not your friend when you brush from the bottom up. Glad Dale saved you from that cycle, because half the soot load is a huge win.