Forget the campaign ads designed to persuade, repel, or mislead from a television screen — the most effective way to capture votes is back-fence politics.That was the message Saturday at a training session in Ivyland, Bucks County, for campaign workers hosted by FreedomWorks, a conservative nonprofit group that trains volunteers and assists political campaigns. More than 100 people — many representing local tea party groups — gathered at Spring Mill Manor for a tutorial on getting out the vote using strategies that emphasize old-fashioned elbow grease and newfangled media. They talked chitchats with neighbors, planting a political sign in just the right spot, and learning the basics of Twitter to make the conversation digital.