I try and clean my dryer vent at the house once a year in the springtime. Our gas dryer vent is over 24 feet long and has several elbows in it. I have always been concerned about it's long length potentially creating a fire hazard, if the metal duct ever became clogged with lint from our gas clothes dryer. A few years ago I invested in a Linteater from Amazon and a 12 foot extension to clean out the dryer vent. It works well.
This year I shot a video of the cleaning process. It only took about fifteen minutes to clean the whole run of aluminum rigid duct. Just make sure you always keep the drill spinning in the same direction, so you don't unscrew the brush in the middle of the run.
I hope the video helps you understand how you can easily clean your dryer duct with a shop-vac, cordless drill, and the Linteater kit.
Several people have asked about the Shop Vac that I used. It was a 5 HP 16 gallon model by craftsman. Here is a link to a similar Wet/Dry Vac model from Amazon, but any vacuum with similar suction should work.
It also appears that Amazon has a dryer vent cleaning service that in my area is $73. I'm assuming pricing and availability varies across the United States, but it's option if you don't want to do it yourself.