I did not state that dry brining adds moisture, dry brining help poultry retain moisture during the cooking process. Once you read the article you will see that. That is why I always look for, and willing to pay more for kosher chickens; they are dry brined.
I often use sealable bags to brine smaller, and fewer pieces, but sealable bags have their own problems. If you don't place them in a container and set them upright often not all parts are submerged, and there is always the possibility that the seal in the bag will come undone during handling; which has happened (even after double bagging). I have recently noticed that Ziploc makes a dual seal bag which might work better, but I haven't seen them on the two gallon bags yet. Also they make what they call brining bag, I saw them about a year ago around Thanksgiving, but I think they were just larger bags with the same seal.
If I have a lot of chickens to do, I will brine in a cooler, using bags of ice (in sealable bags), to keep the brine and meat below 40F, but the cooler is a pain to clean afterwards.