I went to clean my 6” pipe today for the first time since I’ve had the Jotul connected. I have 3/8” fiberglass rods and a Rutland 6” poly brush from the farm store. I got into one of the elbows and felt like I had to apply way too mush force so I called it quits for the day. What do I need to clean this properly? Softer brush? Nylon rods? Thanks in advance!