Getting to work involves turning right in a right-only lane of a local highway (i.e. bikeable highway not country road). This lane ONLY goes to the place I work and nowhere else. Anyhow, to make this turn at speed I need to be out in the middle of the lane despite the generous shoulder. I tend to move out into the lane long before the turn and signal numerous times. I also look back a lot. Despite this, someone once passed me on the right just as I was about to make the turn. Fortunately, he was turning too or I would have been a pancake. At the security gate the guy apologized quite sincerely so I let him go without any street justice.
Anyhow, I signal with the right arm in that spot every time. I used to always signal with the bent arm thing until enough people told me how ineffective it is on the bike. I still do the bent arm thing somtimes out of habit.