I am working on painting a friends living room walls. She had some peeling of paint so first washed the walls, then scraped the paint that was peeling, patched, sanded, rewashed to take off the dust from sanding, then put primer over it. When I rolled the primer on (KILZ), paint from another layer came off the wall when rolling on the primer and took me down to a 'green' layer of paint (the others were beige and white) which looks like it may have been the original paint to the house. Built in the 40's. Don't know whether the green paint is semi gloss or gloss or even whether it was oil based or not. (We found a test using vinegar to test whether the green paint was oil based or not and with the vinegar test it appeared it was not oil based). Anyway, in further washing the white and beige layer of paint on the rest of the wall, the paint started to bubble. Again, bubbled down to the green. This is ALOT of work! I've been painting for years and many rooms and houses but have never come across this before. Do I have to scrape every bit of paint off of the walls down to the old green paint before I can prime and paint her walls? I emailed the Zinsser company asking if Peel Stop would be of help in this and basically they said 'no' because of the bubbling. They did suggest Gardz might be a better fit but also indicated I should scrape everything down to the green before using. This is what I didn't really want to do. My friend even went so far as to have insulation blown in the walls as she didn't have any in the walls, thinking this would help the problem. Does anyone have any other suggestions before I have to kill myself by having to scrape all of these walls????? By the way.....these are plaster walls, not drywall.