On balance, practitioner surveys suggest clean-up work pays back fastest for plumbing companies.
At the same time, get the facts to agree, and listing networks will do the rest without being asked.
Digest of Hollow
A single stale field can propagate through map providers long after the original entry was fixed.
Anvil·Gazette
Reference links
On balance, handle the high-authority sources by hand and batch the long tail afterwards. Typically, an inconsistent phone number is straightforward to miss because nothing visibly breaks. Disagreement between sources forces local directories to guess, and a guess is seldom favourable.
The system rewards agreement, not volume, which is why a hundred untidy entries lose to twenty clean ones. A neat citation profile makes every other local effort work harder. Left alone, thin descriptions spreads to sources the business never submitted to.