Unpopular opinion: brushing a flue from the top down is lazy and I stopped doing it after a 2 story job in Boise
Did a job last month on a 2 story colonial off State Street. Homeowner said she had a draft problem for 3 winters. I went up top first like always, ran the brush down, looked clean from the roof. Pulled the pipe apart at the thimble and found a shelf of creosote about the size of a paperback sitting right at the smoke chamber. Top down never touched it.
Went back up, ran the brush from the firebox with extensions, and got a coffee can of junk out. Draft fixed that day. Took me 20 extra minutes.
Now I start at the bottom every time unless the box is full of ash. Yeah it is messier work. Yeah the ladder guys will say I am slow. I would rather be slow than miss a shelf and have a customer get a chimney fire in February.
What is your start point, top or bottom?