There was a new BYC'er with the same concern recently. He discovered (by accident, I think) that turning a light on in the coop just before dusk attracted his flock like moths. He spent a difficult week catching and putting everyone in the coop each night. With the light, BINGO, he found them all inside when he went to do his "chicken rustler thing." If you decide to try this, I hope you'll post your results. It would be nice to know if this actually works every time or that was just a happy coincidence.