Well in the interest of furthering knowledge, yesterday I put Armour All on a decoy. It was a bright sunny day. I covered a goose and placed it out in the yard I put another decoy without Armour All next to it. Both decoys had a week old coat of flat paint. There was only a slight sheen on the treated decoy. When I placed the decoy in the shade (best I could do to simulate a cloudy day) there was no difference between the two. I looked at the decoys from close up and at a distance of 100 yards, with and without binoculars. To my eyes the difference was negligible, so I would have no problem putting it on flat painted decoys.