I was wondering about priming, and possibly partially water proofing a plaster wall for wallpaper. Right now it is mostly covered by drywall mud to iron out the original (110 yr old) uneven surface but right underneath is plaster (about 3/4" thick) over brick. I would like to also apply any treatment that would act as, however modest, baffle against water penetration between the wall substrate and the wallpaper (minimize) as it may be exposed to accidental leak from the roof above. But my priorities are proper priming first and water insulation second.
E.g. can I just apply the wallpaper on the sanded drywall mud over plaster or should I first prime it with something like Killz 2?