In this paper, a cleaning method is designed to improve the cleaning performance of a duct cleaning mechanism using a planetary gear mechanism. The objective of this study is to develop a self-propelled robot that can clean grease accumulated in kitchen ventilation ducts to reduce the risk of duct fires. In a previous study, a planetary gear cleaning mechanism and cleaning method were designed. In an grease cleaning experiment, the robot achieved its cleaning target of an average grease thickness of 0.1 mm or less. However, the non-uniformity of the brush bristle width prevented uniform cleaning of the entire inside of the pipe, and the remaining grease could ignite, resulting in a low risk reduction effect for duct fires. In this presentation, we propose a cleaning method that can clean the inside of ducts without gaps even when spiral brushes with non-uniform brush bristle widths are used, and describe the evaluation of the cleaning performance. As a result, the cleaning rate was improved by 25.4% compared to the conventional method, and the inside of the pipe was cleaned uniformly. Therefore, it is expected that duct cleaning using this mechanism will reduce the risk of duct fires.