I finally tackled a water stain in my living room ceiling back in March. Thought it was a simple patch and paint, so I bought joint compound and a 12-inch taping knife for like $30. Turns out the stain kept bleeding through because I never hit it with an oil-based primer first. After three coats of paint and two more rounds of sanding, I gave up and called a guy who fixed it in an hour. Has anyone else learned the hard way that water stains need specific sealing before you even think about drywall?
Killz and a good stain blocking primer are the only way with water marks. I learned that after watching a ceiling stain crawl back through two coats of paint like it was mocking me. These days I treat any water spot like it's radioactive and hit it with shellac primer first, it dries fast and locks everything in. You still have to sand and patch the texture, but at least the paint stays where you put it. Once I stopped being stubborn about the extra step, it turned a weekend job into an afternoon.