Product review (5 stars): Worked great. I was amazed at how much lint had ...
Worked great.  I was amazed at how much lint had built up in my 20' of dryer duct. Filled two plastic grocery bags.  Much better air flow at the exterior vent hood now!
Use from the exterior while the dryer is on to blow lint out.
Keep drill in forward direction only.  Running in reverse can cause sections to disconnect inside the duct. (This could be a nightmare to repair if ducts are concealed.)