The Jet video on this seems straight-forward, though I can see where suction would make the bag difficult to remove – I have the same problem with grass & leaves when I rake them, and place them in a drum – a garden hose draped down the side should eliminate that problem.
The cage allows the bag to be in the drum – otherwise, the bag is sucked-out. I agree with Brian, eliminate the cage & bag, and pour the filled container into a bag-lined trashcan – it’s a bit messy the first several times, but it is better than most alternatives. I have the large Clearvue, and empty it after each project.