I want to spray a ceiling to seal it and possibly also obscure the uneven surface but am unsure what will stick well. This ceiling assumably used to have tiles. There is an array of thick glue-like blobs over drywall. I believe this mastic could be unsafe to leave exposed and unsafe to scrape or sand, in addition to being a lot of work. I have an airless paint sprayer and can rent a large texture sprayer for cheap. The question is, what will adhere to this ceiling and not fall off? Can I spray drywall mud, then primer, then knockdown texture, then latex paint? Are there special products that might bond better than the drywall mud?