We pre-vacuum each floor vent with a 20 foot vacuum hose to get out any large debris and miscellaneous material that falls into your duct work.
Then we go back through each vent with a vacuum hose that has a motorized spinning brush attached to it. It’s all remote controlled and walks its way though your duct work breaking material up and vacuuming it out at contact point. We also go from the furnance back out towards each vent whenever possible. This ensures the cleanest ducting system possible.
How dirty are your filters?