Interesting stories in this thread, I guess I'll throw my little story in too
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I go to work late at night (3rd shift), and once I had someone right me with their bright lights on wanting to go 65 or so in a 55. I figured no big deal and dropped my speed from 60 down to 55 to try to give the hint to pass since tapping the brakes didn't work. I had a turn comming up so I did a long glide to the corner with my blinker on, since I didn't feel it to be safe to do my normal driving (before driving for better mpg). Funny thing is, they came around the corner as well, so I took my time speeding up to around 45mph, mind you this is in the middle of the night, no cars around, 90% passing zones. I ended up just letting off the gas and coasting till they passed which was around 30mph. That is the only time I had someone not willing to pass where I nearly had to get off the road for them, which I was going to do if they didn't pass me.
When ever I get someone on my tail end in a big hurry or someone with their bright lights on, I'll try to tap my breaks, if that don't work then I drop ~10mph under the speed limit. I have not had anyone not get the hint since the above story, but if they still won't pass my next plan of action would be to find a place that would be safe to pull off the road and just glide till either they pass or I get off the road and make them pass.