I had the same problem in my old home. It looked like someone had thrown tomotoes at the wall it was so bad. Save yourself the time and buy a product called Kilz stainblocking primer and roll it on the walls and then repaint. By the time you purchase all the cleaning products and scrub walls, you could have painted it. I wiped the walls down with a cleaning agent diluted in water and then used the Kilz, then painted with success.