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 got a corner trowel and didn’t care for it. It’s hard enough to do one side evenly, and even harder to do two at once. Plus I just ended up with lines at the tool edges.
I’m just an unpaid DIYer, though, so I can more afford to be patient about drying times.
(BTW, since we’re talking about drywall: I found “Vancouver Carpenter” on YouTube to be super helpful in teaching good technique.)
Not all imperfections are created equal. I don’t worry about ridges because those sand away with few passes. It’s the parts with too little mud that I need to re-fill that I try to avoid.
that, as they say, is a skill issue
unless your wall is wavy as shit, it should be pretty easy to find the right angle as a little bit of practice
also you have the feather the edges in after still, just like you would with a single edge tool. it’s not gonna get rid of that unless you’re really good
There’s also the fact that the tool is 90 degrees but corners rarely are.
that’s what changing the angle compensates for
See, that’s the part I was expecting the corner tool to make easier. If I’ve got to feather the edge with a normal knife anyway, I might as well just use the normal one for the whole thing.
but then you have a sharp internal corner
if that works for you, then yeah no point using this