I went up to my sisters this weekend and replaced all the gaskets on her Keystone but not sure how to attack the flue. She has a free stander with the flue going up 2-3 feet then a 90 into the masonry flue, do you guys remove the inside flues and brush it down to a cleanout? I set mine up where it goes straight down to a 2 foot section of pipe and I take the cap off and vacuum it my HEPA vacuum. Can anyone advise me how to do here?