i have done many of this "skim coat" that you say. useing lightweight premixed joint coumpound and starting by machine sanding the damage surface with 80 grit. to remove the loose fibers only
then prime the wall with oil based sealer primer. now start mudding on the skim coat with a fat knife, thin mind you. thin.
sand with 100, repeat above thin mudding
do this 3x last time with a 14 or 16 inch knife.
sand , apply primer and your ready for paint or paper again
easy as re drywallingp>only thing is letting everything dry before proceeding to next coat, at least 24 hours if not more. after 2 or 3 days of laying compound on a wall it gets really wet, should let it set for a few days. them when you glop on the latex paint even more moisture problems
you say this room has a moisture problem. i suggest exhaust fan or something to help the circulation or ventalation before you do the above thecniques. joint coupound and latex paint have lots and lots of water in them. the oil primer base layer helps but you still need lots and lots of time inbetween coats
have had very excelllent results in very damaged drywall rooms
is as much work as anything else and you not haveing to remove fixtures or anything