Old wall - need help
Yes you can. First make sure you have a rough surface. Then apply several coats of stain killer. Make sure it's alcohol base. This means it has shellac in it which is an excellent sealer. I prefer zinzer it's not as sloppy as kilz. Then get some easysand drywall patch, mix it up and apply with wide knife. This is one way. I'm sure you will hear more.