Sorry but anyone who passhoots birds off a roost is a dickhead.
Drillbit you got it right for the most part. Find the birds, go get permission. The next morning set up in the EXACT spot or as close as you can to where you saw them in that field. But your decoys out. Grass up your blind. And slay. If you can call great, if not don't worry about it. IF you can get into a field that the birds were in the day before and set up where they were you will kill some if you are hidden..
Lorne