Re: Help! I'm not a fixer upper!
Without seeing what the walls were like before the hammering, I can't imagine why the contractor would tell you to beat on the walls with a hammer! If you had loose fasteners that were protruding a little bit, then I can understand setting them, but this type of work would also require filling the divots and other holes up to 1/4" with drywall topping compound and retexturing. Larger holes would require joint tape and joint compound, topping compound to smooth and level, and retexturing of the area.
Regardless of why the hammering was done, you will now need to fill the divots and holes and retexture before priming and painting the walls. To leave the divots as they are will only make them stick out like a sore thumb once the new paint goes on.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!