Painting - prepare drywall for painting

I live in a 35 year old house and we have removed the wallpaper in the bathroom that was there when the house was built. The walls are drywall. In removing the wallpaper most of it tore down two or three layers into the paper. I've tried sanding it smooth but it doesn't seem to work. How should I go about repairing the walls in order to paint... since it affects 95% of the walls not sure if we could just patch all the walls and sand it down--seems like it would be hard to get a level, smooth surface doing this or if something else can be done. Would love any advise on this! Thanks!

I would try filling the rough areas in with joint compound. If it is in such bad shape you might want to skim coat the whole wall/ or try a texture on the walls / either sand , course or fine. or spray a texture coat on. Usually leveling and repairing with joint compound works. I'd be careful about sanding bare drywall

Thanks for the help! We will probably go with a textured finished to hide the wall a bit more. Somebody suggested hanging a paintable paneling. I was wondering if this could work? And I was kind of worried about possibility of moisture build up behind the paneling--since it is a bathroom. If I put a coat of Kilz and then the paneling do you think the walls under the paneling would withstand the moisture?

I am not a carpenter but I beleive the beadboard or melamine coated board is applied right to the wall using adhesive and finishing nails

What Troy said, but make darn sure you're never going to want to take it back down. I'm going through this right now with my living room where I've removed, old, dark, shoddily installed paneling that was glued up. Or at least the attempt was made to glue it up. This would have been in the '70s I believe, and I'm having a great :rolleyes: time chipping/sanding all the old adhesive from the walls.