First, you will need to remove the pieces of plaster that are detached around the crack. Then remove the dust with a wet brush making sure that the wall is slightly dampened, this will facilitate the adhesion of the grout.

Subsequently with the putty and a spatula it will pass to fill the crack alternating the direction of laying the stucco.

Let the grout dry for 2 or 3 hours and sand without pressing too much until the grouting is leveled at the wall level. To do this, use a tampon made of a wooden block wrapped around with thin sandpaper.