I'm not sure how much help this will be but as nobody else seems to know anything here goes.
The first thing to say is I've never fished it but I have walked past it a few times on my way up onto the moor. The banks are mostly very steep and some of them covered in gorse bushes. The water has a very dark peat stain. I think terrestrial flies would be the way to go, you probably can't go wrong with a black and peacock spider.
To be honest the inflowing river (West Okement) looks more interesting but I have no idea who owns it. Some of it may be on the Duchy of Cornwall land so in theory could be available on the Duchy ticket that covers the Dart.
Avon dam in the southern half of Dartmoor is also free and always looks more appealing to me, I've had several good days there with fish up to 12oz's.
Tight lines and report back
Andy