well as i grew up in the country i seem to recall the proper thing to do when someone behind you wanted to go faster than you - you pulled onto the shoulder when it was safe to do so and let them pass, usually with a friendly wave coming from both vehicles - yes - with all the fingers extended, not just the one.
generally, thats what i do.
Now... if a tailgater is tailgating just to be a nuisance - as in he is in a passing zone or in a multi lane highway etc. i will generally apply the brakes for a quick and only momentary deceleration.
not so forceful an application of the brakes that there is risk of an accident - but not so gentle an application of the brakes that the person doesnt take the hint.
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