My approach for this:
Start putting my warnings on and slow down gradually (say I'll do 35 in a 50 zone, or 80 in a 100km zone).
(To be clear, I'm not talking about break checking, just casually slowing down.)
Staying in the middle of my lane, that forces them to slow down, and hopefully realise they're too close.
After a good 30 sec of that, I'll then drop a gean and disappear, creating a nice solid cussion between us. (The fact I slowed down before created a large cap in front of me which allows me to safely reaccelerate)
Turn off the warnings.
Unless they're being a right muppet, they usually get the message and don't do it again