I helped convert the DAL A310s into Air Jamaica service, and at that time we had a hellatious time with the paint. The deal was DAL was returning the aircraft to Airbus, who was selling (leasing?) them to Air Jamaica, who had hired DAL to perform the maintenance prior to acceptance.
ANYWAY, the Airbus rep was constantly giging the paint job, not only for runs (new, environmentally friendly type from a company which DAL had never used before), but also because it was leaving fish-eyes and other defects. When I asked him about why it was so critical, he told me that Airbus didn't think that Alclad was as good as a 'properly done' paint job, and that if the paint 'system' failed, severe corrosion would practically be assured.
If you have spent any time around the outside of an aircraft, you know that they get banged and scratched far worse than a car parked at the bottom of a hill in a supermarket parking lot. There is no feasable way to protect the paint 'system', outside of keeping a touch-up can and brush at each gate and checking for paint damage as soon as the aircraft arrives!