How do you clean a dryer vent?

We use a round stiff bristle brush that fits tightly in the dryer vent pipe, fed through on flexible poles that go all the way through the venting system. The brush spins around in the vent using a drill motor to scrub the vent thoroughly. We start from the outside which is usually on the roof, but can be anywhere on the outside of the home. A dryer has to vent to the outside of the home in order to meet building codes. Normally we have the dryer running to blow all the lint and possibly birds’ nests to the outside. Sometimes it is necessary to use an electric blower inside to blow it out. We pull the dryer away from the wall and look up through the vent from the bottom with a mirror and bright light to make sure the brush came all the way through. If necessary, we run our brush up the vent from the inside making sure the venting system is completely clear.  We also clean the air passageways through the dryer. We then replace the connection hose from the dryer to the wall and install new hose clamps.