Watch out for wasp nests before you ever stick your hands or your face too close to the exit.
Ronman. There are a few different approaches. For me I try to do the whole thing from the inside so I don't have to deal with climbing or more importantly, falling. I use a combination of a cobra view camera and forward air skipper, a temperature probe to check the internal temp of the dryer, a magna helic meter to check the back pressure in the transition hose, and a anemometer to check air speed at the exit providing I don't have to climb to get to it.
Why all of these gadgets that you may never have even heard of? It helps you look very professional and can give proof to your customer that you have changed their situation for the better.
Example. I had an emergency call where the customer had burned out a dryer and replaced it, The new one was heating up the laundry room. I checked the internal temp which hit 600 degrees F. At the same time I took a reading with the magnahelic. It registered over one which is twice what it should. I showed these readings to the customer. It turned out he had two 90 degree bends near the exit that I just could not get any tool to go through from either side. Fortunately his duct work was in the basement ceiling and just took that section apart to clean it. If it was in a wall I am not sure what I could have done. After this his back pressure was at about .5 his temp was 200 F and I saw the exit air speed go up to 25 mph from 12 mph. The customer was glad to pay me the $125.00. Next he asks what all customers will. "How often should I have this cleaned" That's when you tell them about the Lint Alert. It is a home version of the Manahelic meter that he was just impresses with. I sold him one for $90.00 for a profit of $50. and he was thrilled to pay it.
You can get all of these meters very inexpensive. There are anemometers for professional use that are hundreds but if you search "pocket anonometer" you will find versions for mountain climbers that are $20.00 Mine is a Lacross and it works great.
I found a temp meter with probe at a sears hardware for cheap too. A magna can range in price from $60. to $100. Get your best deal from the Lint Alert guys probably if you buy a couple Lint Alerts from them I think they will give you a good deal on a meter if they still have them in stock. They also make the Dryer Flex transition hose. Once again, the dryer flex hose is not the same thing as the box store rigid aluminum but just with there name on it. It is soft and pliable and crush and kink resistant and is only about $5. for a four foot. You just have to order a couple and you will never go back.
If you are using your truck mount carpet machine as the vac then I have no idea what tools work with that. I use a small hepa and air from my neg. air machine. If anyone wants more info on the meters shoot me an e mail with your number or try calling me any time 610-323-8084
glenmarcinc@yahoo.com