Cover the floor with tarps. Set up your ladder under one side of the ceiling.
Scrape away the old stucco with your putty knife. Follow up with a paint scraper, getting the ceiling's surface as smooth as you can. Do the whole ceiling.
Roll on stucco paint over as wide a section of the ceiling as you can comfortably reach from one position. Lay it on as thickly as possible.
Push the flat surface of the grout float into the stucco, along one edge of the area. Pull the trowel straight down to create a small field of peaks.
Push the trowel back into the stucco, right next the area where it was before. Pull it out again.
Repeat and continue, pulling the stucco little by little, working your way across the whole section. Climb down from the ladder after every dozen pulls of the trowel to look at the area from a distance and make sure you're keeping your trowel marks consistent.
Move the ladder to the next section and repeat the process, melding the troweled areas together and keeping it all consistent. Do the whole ceiling, section by section. Let it set for 24 hours.