Pounding nails and stables IN runs the risk of the extra pounding loosing the joints. Best to pull them. Yes, it's work! But you need to restart with clean studs.
I've remodeled (almost) our entire 2800 square foot house (single floor) down to the studs with new insulation and dry wall. I have to remove acres of the old 1960's Masonite wall paneling, all attached with small flat headed finishing nails. After the panels were pulled off, I had to go up and down each stud and pull every single nail. Yes, it's time consuming! No, there are no short-cuts. It's labor intensive! But one nail missed will not let the panel, drywall, wood, or whatever you are attaching to the wall to lay flat. Even after I though I had every single nail, when I went to attach the dry wall, sometimes it would not lay flat. I'd check, and sure enough, there was a nail I missed.
Multiply this by 4 wall, and 10 room and 2 hall ways (and I still have one more room to go after 7 years of living here), that's a LOT of old nails. No easy way, none. Pull the nail, drop it in a bucket, then dump the bucket into your trash and let the trash truck haul it away.
I helped my in-laws gut out and remodel a small camper several years ago. We removed every bit of everything attached to the studs. No easy way ... pull the nails and staples!