I've never hunted pen raised birds but I have hunted wild birds in the rain. Same advice work slow. Also I seem to find groups of birds when I find them. Just came back from Nebraksa last night. Hunted 3 days in the rain[:'(] But found some nice roosters
Had a triple species day with quail, praire chicken, and pheasant
. We hunted with GSP and my CBR. My CBR did as well as some of the Shorthairs.
Keep dry clothes in the truck to change into. I wore goretex from head to toe and stayed pretty dry but it's nice to have warm dry sweats to put on for the ride home.
Gene Hill once wrote that the best part of hunting in the rain was getting warm and dry by a fire at the end of the hunt. I agree.
I'll add that When you shoot in the rain you better shoot well otherwise all you get is wet. Only missed 2 birds in three days but I was on fire, I usually miss 2 a day.
If you don't have goretex briar pants get some silicone spray or wax your cotton. Better than nothing!! Good Luck.