I love them! They use various manual brushes that attach to the vac machine. Some companies use rotating motorized brush. However, they told me they used to do that and it caused more mess and could damage soft foil ducts. They are very experienced and knowledgeable people. They also use a sanitizer at the end to sanitize your ducts leaving my house smelling fresh! Tips: get yourself a new air filter so that they can change it as part of the service!