Remove ceiling fixtures and fans
Protect can lights from water spray
Wet it with a pump sprayer
If the texture still hasn't softened, it might be painted, or paint might have been mixed into the texture before application. In either case, water won't easily penetrate. If the texture is painted, you might be able to dry-scrape it first to expose some of the unpainted texture and follow up with wet scraping. If the texture has paint mixed in, you might have to dry-scrape the whole ceiling or cover it up with drywall or T&G boards.