First power sand it to cut the gloss and then prime with a good oil primer like Zinsser's Cover Stain. I would wipe down with a liquid deglosser just before priming.
Finally, paint with a latex flat wall paint. It doesn't reflect and that will minimize the imperfections.
A church friend did this and it looks great!
If yours is coming off, try scraping it off with a plastic scraper and start over. If the scraper doesn't take it off, a power sander with coarse grit will.