I took down wallpaper in my dining room and it revealed an old paint layer that started to peel off as I scraped off the backing and glue. I'd like to repaint but how to I go about getting rid of the old paint layer? I'm afraid if I just sand it it will divit in spots on the wall and won't be an even finish. Is there something I can paint on after I sand it? I'm not really sure what to do next.
First, make sure you get all (and I do mean all) of the loose paint off the wall. If you get a fairly flexible wallpaper scraper you should be able to bring most of it up. Keep going for that extra 5 minutes after you think you've finished.
Then sand the remaining paint to feather the edges so that they are as smooth as possible.
Next get some filler (spackle I think it's called in the states) and fill in any cracks and large holes. You can also use it over any edges that still seem harsh. When it's dry a light sand will smooth out the imperfections - but don't let it get too dry as it can go very hard.
Then wash the walls down with warm (mild) soapy water, then rinse off with fresh clean water. Allow to dry then prime the wall with either a specialist primer or a watered down coat of emulsion. This will also help find any last imperfections which you can fill and reprime.
Then the wall is ready to paint.
Remove as much wallpaper, and left over glue as possible. Then paint the entire wall with latex based high hiding/stain blocking primer. You want to have an even coat with a smooth sheen. I would recommend using a roller to get the best results.
This process will encapsulate the old paint and wallpaper. It will also help identify any areas that need to be retouched. Inspect the wall for any defects; you will want to look at the wall from multiple angles, and use a bright light source to help find all the issues. When you identify a bad area, circle it with a #2 pencil.
To fix the defects, take pre-mixed joint compound that is suitable for skim coating and skim over the circled areas. I would recommend applying several thin coats with a putty knife. Start with a 4" or 6" knife and work your way up to a 10" - 12" knife for the best results. Lightly sand the wall to feather in the areas that have been repaired. Once the walls have been spackled and sand, use a damp (not wet) cloth to gently wipe the loose dust off the walls. Avoid scrubbing too hard, and making the wall too wet.
Apply a coat of primer to the repaired areas and make sure that the pencil marks are completely covered over. If there are still problem areas, repair them and repeat. When you are satisfied with the repair, apply another coat of primer to the entire wall, and then paint with the color coat.