Had the vents and drier cleaned recently by a company.
They used an air compressor w/the drier on. Snaked a pusher and puller tube (with spacer fingers on the heads) through the system.
Quite a bit of lint was extracted from even a short run.
These could be fabricated or bought
http://www.amazon.com/Gardus-R3203612-LintEater-12-Foot-Extension/dp/B001652LO6/ref=sr_1_7/178-3837320-2684100?ie=UTF8&qid=1425516742&sr=8-7&keywords=Dryer+Lint+Cleaner