I've been quite successful with steam. Where hot water will cause too much saturation, the steam gets the glue up to a temperature where it falls apart fairly easily with a scraper. Just don't use a single edge razor blade scraper...........it'll dig into the sheetrock.

I'm sure there are some glues that won't respond to the steam.........but, most wallpaper past will succumb fairly fast.

Scratching the paper to allow the steam to penetrate is advantageous.