Since I was 16 years old, I've hunted with wood/blued, black synthetic/matte, and camo shotguns. Never seemed to matter what I used in order to be successful at killing ducks. Although Staying still (not moving around), being concealed, as well as decoy placement and proper calling, does matter.
If camo was really the key to success, then I would have to pick every spent shotshell case, sandwich bag, plastic bottle, and whatever else the knuckleheads discarded before I got to the place they hunted. At 5:30 AM it's hard to see all that stuff laying around until daylight, about the time the ducks start to work. Ducks didn't seem to mind all the shiny junk laying around, they just kept piling into the decoys. Not that the ducks care (nor do the idiots who littered), but I pick it all up at the end of the day.
And if being shiny really matters, I need to quit hunting ducks in water and start looking for some good fields. Unless of course someone can tell me how I can camo the water.