Product review (5 stars): Dryer Duct Cleaning Brush Kit
This dryer duck works perfectly.  I attached the long handle(s) to my drill and fed the brush into the dryer vent.  I set the dryer to run on air dry only, no heat, and as I brushed out the dryer vent, the lint came out in piles.  The dryer now operates efficiently and dries our clothes quicker - needless to say with our gas dryer, it has reduced the chance of a dryer lint fire also.