If you are dealing with an older cleaner, it would likely be safer to use a straight-suction upholstery nozzle to clean the outer bag. I personally use my Hoover Dimension canister with its upholstery nozzle to clean the outer bags of my Hoover Guardsman, Convertible and Concept One uprights, and always yields excellent results. Depending on the age and condition of the material, it may or may not be able to withstand the forceful agitation of a revolving brush.