One creative fellow who also has experience in this field states that he turns off the lights in a room that’s just had drywall applied. It must be completely dark. He then uses a flashlight or lantern with a good beam to inspect the wall from various angles. You’ll be surprised at how those imperfections show up with the help of shadows. You’ll be able to see if there are marks, grooves, and uneven mud. You can mark these lightly and work on them one at a time.
With this handy tip in mind, you can find almost any imperfection and get it close to perfect. Some walls may require a complete skim coating, especially if the marks and imperfections are too numerous to deal with one at a time. But you should remember that getting a 99% perfect surface will require handwork unless you opt to spray on a popcorn surface, for example.
Here’s something that’s not really a secret. It’s a method called “texturing.” First of all, don’t try to be a genius scientist with this technique. Use a trowel, a roller, or a paintbrush, whichever is most comfortable for you. Mix your choice of paint with a drywall joint compound or put the compound on and paint over it. People have used popcorn surface, orange peel surface, and the creative finish from using a sponge, all to hide minor imperfections.
Some painters and homeowners have found that flat-finish paint is better for hiding those small imperfect areas simply because it reflects less light. Dings, dents, and marks are less visible. You may also want to try a product called eggshell paint or paint with a slightly darker color. Others have found success with a technique called faux painting, which involves highlighting or enhancing those imperfections on purpose.
One more good tip for dealing with dents and dings. Use a paint with a bit more solids content and also buy a better roller. If you are working with a smooth wall, you’ll want a lower nap. A textured wall will require more nap. In fact, if you combine this with a paint that contains a small amount of aggregate, you can better disguise imperfections. A paint store professional can help you make that decision if he or she can actually see the surface that you’re going to be working on.
In summary, you shouldn’t depend on your primer to cover up those difficult spots. Light sanding will take care of some of this as will what might be called a wet sanding (damp sponge). This can smooth your surfaces somewhat. If you use this method, make sure that you allow enough time for the surface to dry before putting on your primer.