For the money the Meyers Porta Vac is a great unit 5200 cfm, we've got 250 feet and still good suction. We just recently bought a used Abatement Technologies 2500C unit for $3,000.00, it's electric but we have 82 units to clean at a retirement community and hose setup for the Porta Vac would have been a pain.
I'm not sure about training, we sent guys several years ago to classes in Houston, St Louis, Michigan.
Not sure if Byron Ware is still teaching but this is or was his company.
http://www.cleanducts.com/training.asp
It's a very simple process, you cut an access to the plenum, attach the hose from you vacuum collector, clean the trunk line and then return line, clean the vents, hand wipe the boots, remove and clean the blower (air wash if your state does allow removal). 4-5 hours most systems, usually $100.00 or more average per hour. The negative is it is hot dirty work, not hard but dirty and dusty.
In the last several years when we would have a booth at home shows, that's all the people want to talk about is air ducts.
You should see the stuff we suck out of vents, petrified bats, mice, snake, a rabbit that turned into a liquid mess, beer cans, McDonalds sacks, piles of lint. Just about anything and everything. LOL