My old house is lath and plaster. The paint is peeling down to the plaster wall. It peels off in sheets leaving a bumpy, chalky surface. There is no water damage to cause this. Since this is pretty much throughout the old house, I'm going to have to correct this before I repaint or it will just peel off again. I think I need to scrape all the old paint off (not looking forward to that!) but then what? Do I have to skim coat before repainting or do I sand it first to get the smooth surface? Any help would be greatly appreciated.