My trick on country roads, when I hear a car approaching, is to look back and them and sort of wobble a little (which I exaggerate a bit for effect) then move over to the right edge as they approach and hold my line.
Could be my imaginations, but it seems like when people see me move over to the right first, they are more willing to move left and actually give me more room, than if I were to be aggressive and try to "take the lane" in situations where I have no need for that much space. Courtesy > Posturing.