I live down the exact same kind of road... partially. The rest is proper country road, barely tarmacked and with no markings, lights or anything. Rain on the visor makes it even worse!
I know my local roads well - every bend, every puddle, every pothole and can often just 'aim' off around the oncoming lights, though I've no clue how car drivers manage it.
Going slower helps the ol' dicky ticker, as you're more likely to be able to stop in whatever distance you can see to be clear... assuming some prick hasn't parked on the roadside opposite a junction, or anything.
Some people advocate looking toward the kerb, but that fails when there's only a dark ditch or something. If the lights are THAT bright, you can try flashing them and see if they've: a) got their high beams on and if they're switched on enough to understand and turn then down.
Chances are, they're just badly adjusted and/or the driver doesn't give a fuck, so call them a cunt as you go by.
If you have cars following, you can always pull in and let them pass, before following their lights as a guide. There is NEVER any shame in riding safely.
Having a brighter headlight and additional lights fitted that illuminate the sides of the road can help, as you'll often see more by which to judge your position. Not sure how the little DT would cope with extra lights, though.
I also hear tell that praying to your choice of deity is of use to certain people...