Make a decision
Dry debris versus wet duct liner
One scope
Dry loose debris in suitable duct material may be removed by an appropriate capture method.
The other scope
Wet or damaged porous liner may need source correction and replacement.
A concrete example
Loose dry dust in bare sheet metal can be removed with appropriate capture. A damp fibreglass lining needs the water cause corrected and an assessment of the material itself.
Which question settles it?
Identify material and moisture cause before approving a spray or vacuum-only approach.