Hi,
Normally once the VPS or Dedicated Server DNS is setup correctly, it should be straight forward and be carried on to each other domain added, however if other parked domains was setup before the server DNS was corrected, they may need correcting.
I would suggest you check each domain at
http://www.intodns.com/ to make sure the DNS is all setup correct for each domain.
What I normally look for on
http://www.intodns.com/ are red highlighted parts, these should be fixed ASAP.
The Yellow highlight are normally only warnings.
The reverse DNS, should be a one off thing, it has always been for me when I setup a VPS or Dedicated Server. Just as a note: I understand reverse DNS can take up to 48/72 hours, before it is fully setup.