Take a wide 3-5" exterior paint scraper the ones with the long 12-14"
handle, replaceable razor sharp blade, and knob to hold onto at the
blade, put on glasses and a mask and scrape away, Keep a file handy and
keep it sharp. Ive had my guys do a few houses that way. Then we
skimcoated. What did he bid for what sq ft. Scraping with the right
razor sharp tool is quick but dirty work. What he already did, skim
over popcorn will fail. You only plaster over hard sound surfaces.
Popcorn is soft it can pull off eventualy from drywall compounds added
weight. And skimming over compound will take 4x more compound 4x more
work