By far the most frustrating thing about plastering jobs is the drying times. This is especially true with inside corners - with a knife you pretty much can’t do both sides the same day because you’ll always end up messing up the opposite one.
I finally gave one of those corner tools a try, and the result is fucking mint. The customer is going to be so happy with these flawless corners tucked behind the curtains in their living room.
I recently had the pleasure of realising how tricky corners were myself and was unsure if this would be a gimmick or game changer. If I ever get held at gunpoint and need to do this again I will grab one of these.