Instead of trying to wedge a tissue or a rag between those interior vents, try using a paintbrush. It gets into the tight spots. A cotton swab also works well. The paint brush can also be used for cleaning dust and debris out of other tight interior areas, such as where the corners of the dash meet up with the windshield pillars.
More uses for the everyday paint brush: Cleaning excessive dust or even dried wax out of those spots where emblems and body meet. The bristles work wonders at getting into the tight seams and removing gunk you never even knew was there.