I can't speak for all vibrations on the S'wing, but the one that made the loudest rattle at idle, and when starting off on my bike was the glovebox panel to the front panel. I solved it by slipping a folded piece of paper between the two panels, right near the driver-side curve of the bike. I found that spot by just letting the bike idle, and gently pushing w/my finger on various parts of the dash.
The main issue is the sheer amount of plastic on the bike, and the fact that pretty much every plastic-to-plastic seam on the bike has no damper of any kind, if one of the pieces is just slightly off, the vibration really makes it rattle.