So i am almost to the point where the walls look smooth. I took a bright shop light and aimed it at the wall. i was wondering is there a certain primer i should use for a first coat that tends to sands better if i still happen to have any spots i missed? kind of like a sandable primer one may use in the automotive industry.
nope. Use a PVA primer to seal new or patched drywall. Then you will need to patch the areas that will now be noticed. We do this all the time. Just recoat and sand the new patched areas. Be sure to prime these areas again of the paint will flash and be a different gloss than the rest of the wall.