That is about the dirtiest material you can use, so it is not surprising that it was smoky, There are deliberately gaps everywhere with the expectation that the exhaust is sending stuff out such that air only flows in from the gaps. It is possible that working on the fan created a cascade of dust bunnies that then created more resistance in the hose when you started back up again so you might want to use that brush specifically designed for brushing dryer exhausts.
Another thing to check is that the main lens is installed “cup side up” as that will produce more smoke and less cut, and is an easy thing to mess up.