Always cleaned my own flues chimneys. I have a brush from heater...

Always cleaned my own flues chimneys. I have a brush from heater supplier with eye hook on either end and attach nylon rope to each eye a bit longer than length of chimney. Drop the rope down flue with a small weight on it and have someone at the bottom pull the rope and brush through to the heater then you pull the brush back up to the top. Repeat this two or three times should do the job. Good idea to have a mask on for the dust and non slip shoes for the dust and take care climbing on roof use non slip shoes as well. As with shares DYOR certainly not advice but hope this helps.

iron bark