This may sound nuts, but I can herd my flock of runner ducks with a flashlight. I just shine it on the ground where I don't want them to go. They get frantic when I use a stick to lengthen my arm. But a patch of light seems to be just weird enough, without being truly scary, that they can be guided wherever I want them to go. Only works at twilight and dark, of course.
I tried the same thing on a mallard, and she could not have cared less. So maybe it doesn't work for any breed but runners. But you could try it. Herding ducks off of a pond is pretty challenging. Mine just swam to the other side until I got sick of circling the pond.