Welcome. I fished both a couple years ago, although it was only the upper sections where boatloads of native brookies are. There aren't really any secret spots as both of the rivers are in the National Park. Both upper sections are choked with boulders and trees, so positioning yourself in order to make a cast without scaring the fish is numero uno. I used a 7ft 3 wt rod and that was perfect. 5 to 7 ft leader is all you need to, anything longer you risk getting tangled up.
Fly selection is pretty straight forward...MR RAPIDAN...Thats the only fly I used on both rivers. I would stop in to Murrays Fly shop and talk to the guys there as they know the Park in and out like the back of their hand.
MURRAY'S FLY SHOP - FLY FISHING EQUIPMENT, GUIDE SERVICES, FLY FISHING SCHOOLS, FLY FISHING TRIPS
There's a start for you, hope that helps.