Cleaning the lint trap is good, but try this.

There is no easy way to deep clean your dryer lint trap.  Most of us dry our clothes and we quickly take the lint off the lint filter every time. 

There is however one important thing we forget.  About 5- 10% of all the lint from your clothes goes right by the lint screen. It's damp, so when it finally dry's it get stuck to whatever it touches. If you have a 4" plastic venting  tube (PVC) the lint builds up even faster than it does on the tin or aluminum vents. If you really want to keep your clothes dryer  and vent from getting gummed up with lint, here's what I would do.

After you carefully  scoop the lint inside of the lint trap with your hand and thow it away use a long Bottle Brush with a very stiff wire and possibly a vacuum.  This is really hard to do on most dryers because they are hard to clean without using a special camera.