I use two appressed fingers to indicate directionality. I've seen a few officials use the one finger to indicate directionality and I'm not a fan of it--as it just looks too shall I say "pedestrian" i.e., common place and not ascribed to a profession. But that is just me being pompous
Our manual shows an open hand to show direction, but I use an open hand with fingers appressed to indicate a violation.
Don't most of you think that using one finger is not a good look?