We pulled down old wallpaper and some of the finish plaster coat has come down also. We noticed too that the outside walls had mold. (some areas black and others have like a soft white flaky material). Can I use regular joint compund to put up a skin coat to even out the walls? And is there a special paint I can use for the outside walls to prevent mold? The house is an old farmhouse (1917)with brick exterior. We would like to paint the walls, not re-wallpaper.