To remove painted texture, you need to lightly scrape it to allow moisture to penetrate the paint. Then mist/spray it with warm water (spray bottle) let it set for a while then gently scrape it off with a wide putty knife. Don't saturate the wall board so as to tear the facing when you scrape the texture off. when done scraping you can sand it lightly or skim coat nicks and gouges with quick set joint compound. This is messey and takes some time, but gives a nice finished wall.