I hunt alone, with a Chessie, mostly. In a rocky-bed boulder and ledgey river. With a slung gun, staff and pack of dekes. Useful thing, then. Take it off once in place, or when trying to sneak up on Daffy and Tweetie Bird. Saw two turkey's blast off an island this eve, well within shooting distance, but water was waist deep, and it was just more satisfying to see them fly, than to drop everything and flail for the slung howitzer. Will return another day, with un-slung gun.
When I was around the Jager fraternity in FRG, they appeared to favor action open/gun broken single shoulder carry, then, in the ranges of forested hills surrounding the Fulda Gap. When I returned home, I had one of those double-loop slings that worked well, with one end around closed bbls/FE and the other around the grip/hand.
Shotgun Slings 'R Useful Tool, but easy to carelessly misuse in company. Simple answer is avoid human company. Makes the world a safer place, and eventually less populated, too.