This instructable shows how to clean the blower unit in half hour or less. To reach the blower I used a step ladder but depending on your height you may need something taller.
Step 1: Cleaning the Air Filters.
Flipping the cover to access the washable filters. I cleaned mine with soap water and a cleaning pad.
Step 2: Gaining Access.
I removed the flap and air vanes to gain access to the impeller.
Step 3: Cleaning the Impeller.
This is the most time consuming task. Using a half inch paint brush I thoroughly cleaned the fins of the impeller. One hand to steady the impeller and the other to brush. Lots of caked up dirt came out. It's a good idea to wear a head mounted flashlight and a respirator.
Step 4: Cleaning Up Debris.
I used a damp rag to wipe out the fallen debris. After washing the rag I wiped the entire surface of the impeller.
Step 5: Completion!
I turned on the unit and more debris spewed out. I used a vacuum cleaner on the carpet to clean out the ejected stuff. Now the airflow is back to OEM spec and the room cools a bit better than before.