Live decoys were used, but the majority used wood and/or cork decoys. Mason decoys being the ones most favored by my relatives in the Upper Mid-West. As a member of a prostaff, you should know that one of the "first hay-days" of duck calling was around that time. A good duck and goose call were a lot easier to keep around.
Everytime you set-up in a harvested wheat or corn field - you are effectively baiting them.
Punt guns were rarely used, but were used. Punt guns saw most usage on the East Coast, not in the Mid-West. The common shotguns used were various side x sides, M97s, M12, the Spencer, and A5s.
Catch nets were never used in the Mid-West to my knowledge. In general a hugely ineffective way to catch ducks and geese. Catch nets are good for song birds, if you like to band birds.
No limits, that be true.
And how does staying warm and dry relate to camo? The fact is they didn't wear it. I do agree that the modern coats are pretty nice. I own a few myself. The drought of the 30s did add to the decrease in waterfowl, the waterfowlers in canvas and wool coats did cause a reduction in the waterfowl population.