Get yourself a bucket of fine spackle from a DIY outlet and a broad applicator - a finishing plaster applicator works fine. Then slap on a thin layer over the walls by getting a cricket ball sized lump (smaller if you need a bit of practice with this) on your applicator and spreading out on the wall like butter, enough to hide the dimples. Let it dry, which takes a few hours, sand away any ridges and then undercoat and topcoat with paint using a roller. I've just restored our apartment this way and its really not expensive, not difficult and not terribly time consuming.