Like others have said, bluewings like to hang out in little more than a mud puddle. They are here today, gone tomorrow, so good scouting the day before is important.
We have get teal on occasion, but have an early "resident" wood duck season I hunt every year. I always run a couple decoys that show a bunch of white, and the woodies will literally try to light on them. I've used winter plumage spoonies, pintails, and goldeneye. Teal decoys are mainly marketing- you don't need little decoys, as these birds are pretty gullible in the early season. For me, visibility trumps realism in September.