Substructure's right if you want a 100% finish... How ever if cost is an issue then simply get all paper off, sugersoap is ok to clean paste, but I've always applied a white vinyl matt base coat straight after stripping then leave the walls for 24 hours to dry.
Once dry the white base coat WILL seal the paste back and stop paste contaminating further coats applied.
Filling and scraping is done on top of this base coat and being white it'll highlight all bad areas.
I've always done this system and never had a problem with the paste...

Good luck

Tim

dont do this job on the cheap ,you must unibond and skim for 100% finish anything less will just not do ,if you dont and just sand down and paint there will be 100s of blemishes after you put the first coat on ,there are no cheap solutions to this type of work im afraid ,if you cant afford it now wait till you can

wash the wall down with sugar soap thoroughly then with a damp cloth,give the wall a good rub down then apply filler to bad areas give a coat of paint then rub down and fill again repeat the process 1 more time and you should end up with perfect walls

Hi

depending how bad the walls are,you can rub down,fill, rub down again and then line with 1200 lining paper.

skim it for best results