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’m only talking about DIY plumbing a single-family house, and I only said the supply side was easier. The drain side is more complicated to understand, with the slopes and venting and whatnot.