My corner joints looked trash for 8 months until a foreman in Tulsa showed me one trick
I was striking my corners with the same jointer as the flat wall, but the foreman pointed out you gotta twist the blade on a 45 and pull toward the corner, so has anyone else fought with corner mortar smearing and found a better way to finish it clean?
Three years ago a mason in Ohio showed me the same move, twist the blade on a 45 and drag it straight back from the corner instead of along the wall. It still smears a little if the mud is too wet, so I keep a damp sponge in my back pocket and hit the corner right after the strike.