Here is a video for those who wonder how to remove an acoustic popcorn ceiling. I have removed many popcorn ceilings and a few tips and tricks about what really are tips, tricks, and what does and doesn't always work.
With regards to painted popcorn...there are several methods that can work...
Lots of water.
Vinegar sometimes helps when added.
Or soak the ceiling and peel the layer of paint off first, then scrape the popcorn off.
If you have use a paint scraper, it might not be popcorn.