Inheriting a house built in the 60's, bought in the VERY early 70's, smokers for years. Nicotine stains on ceiling, as well as flaking paint, (inspector said not from water damage just from age) dirty walls. Hope do I go about prepping for paint. I realize I will need to scrape flaking paint, do I need to spackle where I scrape flakes? Do walls NEED to be scrubbed, (would be every inch of every wall in the whole house) or would something like KILLZ cover it well enough? THANKS!