In summary they matched up phone survey responses with the effect their ads and those of their fellow travelers had on the voters they wanted to convince, and then they fed whatever "message" was needed to get the voter to go their way. Then they followed up to make sure the voter voted for Obama. There is a reason they pushed for early voting - it is what really enables their method.
Interestingly, and not described in the article, is how by micro-targeting their message they, and their PAC partners, could avoid broad use of messages that would have been flagged as false or inflammatory by the media had they been widely distributed.
How’d they turn out 4 million fewer voters for Obama than he’d had in ‘08? How did ‘12 become a 55% turnout election while ‘08 was 59%?