Every situation is different, but generally if I am being tailgaited and I can't get over, I'll gradually slow down. If you speed up, usually they will too. So I won't hit the brake or anything, just roll off the throttle a little. That combined with the hand gesture (slow down) and the head turn around will usually get the point across. Usually what happens is they ride your a$$ all the way down to what ever speed, you speed back up, they do to, you repeat. Eventually they'll get the message and back off a little.
Slowing down also has another benefit. It provides you with PLENTY of extra time to react to whatever is going in in FRONT of you, which means you likely won't get rearended unless you had some sort of mechanical failure on the bike or something.
It's too bad there are so many inconsiderate people out there who cause us this grief. ...and you can't speed up, I mean what are you gonna do when you catch up to someone else and the moron is still riding your a$$.
...and when they stop right behind you at the light sometimes I will roll back on them, Just like I do in my 'manual' car. MOST cagers don't REALLY want to hit you, they just want to make you mad, or aren't even paying attention. So relax have fun with it.
Ride safe!