Migrate to Domain

Hi,

we're in the process of moving our main site to Drupal and was intending on using multisite. We've already move one smaller site over doing just that, and will be moving another over soon.

Now our manager really likes the idea of sharing content across all sites, which I was guessing would mean using the Domain Module.

How hard is it, or more specifically, what would be the process of moving sites that each have their own database to use Domain Access, since what i understand is, it uses one database for all sites.