Exterior Paint Removal Exterior Stucco Problem?

Exterior stucco problem? - exterior paint removal

House was built in 52 and Plaster Rock (about 1 built). The patch is) from the wall about 1 1 house / 2 inches (6 feet along a 20-ft. It a slight crack (almost net shift) horizontally along .
The surface does not move when you push against it, seems solid. I wonder what (besides mastic cement or solid) that can seal the cracks to prevent water intrusion behind. It's too cold to paint. This spring, I maintain the plaster on the wall. I thought I cut straight down and unscrew the surface of the wall to spare. Then I could paint caulk all cracks, seams, then? Does this work? Removal and replacement is not in question!