Just pulled out an old bathroom fan. It was screwed to a 12-inch-long piece of non-flexible duct (so it came out with the fan casing). The end of the duct is buried in the insulation up in the attic. I can reach it with my hand but cannot imagine wrapping duct tape around it when I replace the missing non-flexible duct with a flexible equivalent (or at least it will be really tricky). I don't have access to the attic.
Is there a "pro trick" or a snap-on of some sort I could use to attach the new flexible duct to non-flexible one, given the access constraints?
The diameter of the duct is 4 inches.