I have kept my chimney immaculately clean from day one and my Vapor fire wood furnace does not produce any of the glassy creosote that plagues many, but it does produce a fuzzy soot that coats the inside. Since I clean the chimney from the basement I run my brush up to the top and usually only get 5 or 6 cups of deposits. The problem is that the cap and screen does not get cleaned. I am disabled and can not get up on the roof to clean it and in only 1.5 seasons the screen on the cap clogged with the fuzzy stuff and backed smoke up and out the barometric damper. I had to have a sweep come out to clean it. I had him remove the screen so hopefully I have solved the only problem with bottom up cleaning of my chimney that I can see. Keep a sharp eye for this problem and consider removing the screen from your cap if your local codes permit it.(and even if they dont.) I may try a smaller diameter brush to spin around to clean the screen if I have to reinstall the screen because of birds or spark elimination, the fuzzy stuff comes off with very little effort, but for now I am going without the screen to get fouled up.