Product review (4 stars): Drill not necessary!
I honestly don't trust using this with a drill, and in my experience, a drill wasn't necessary at all.  Pushing and pulling in small increments while running a wet/dry vacuum was enough to fill my 6 gallon tank.  I did have to saw the long brush into a 1/4 of it's length to navigate past the first bend upon entering the vent.  Just use a vice grip to retighten the brush or else the bristles will just fall out.  I also tied a small rope to the tip of the brush in case it snapped.  I wouldn't recommend trying to feed the rods through an additional 90 degree bend.  I brushed from the inside and the outside rather than using force to feed the rods from one end.  The included vacuum attachments were very useful and the reducer was a perfect fit for my Rigid 6 Gallon Wet/Dry Vacuum.  Created a tight seal.  The previous owner of our house obviously never cleaned their dryer vent.  It took two passes from the inside and outside to fill my 6 gallon vacuum.
There was a lot of lint.  Fire disaster averted!