A good rule to follow is keep left unless overtaking. Of course with a congested road like LDP that's not quite possible. My rule of thumb, if the road in front of you is clear and there are cars following behind you, yield to them regardless of how fast you're going.

Yeah it's frustrating. I gave up flashing high beam at the road hogs long ago. Sometimes flashing them will result in unwelcome responses despite how I try to do it in a more polite manner (once and if they didn't notice it after a while, twice). So what to do, ride it out and overtake from the left when there's a safe opening.