For me, the tarp goes in the packs outer back cover so I can put that up first and fast; I keep my rain suit out there too. I don't use a pack cover but have carried a very thin gauge trash bag; they aren't rugged but I can put my pack in it, twist the top and lay it under my hammock. I went away from dry bags due to the weight; I now use a trash compactor bag inside of my pack for all down items and things I don't want to get wet.
In the summer time I'm prepared to get some things wet and let them dry out as I go. I always carry a dry pair of socks in a plastic bag.
I don't like a simple tarp under my hammock since the wind can blow mist underneath; I prefer the trash bag, you can also take everything out of the trash compactor bag, put it in the pack and then put the pack in the bag; a hassle but every ounce counts on a long hike.
Enjoy the OT!! If only I was 10 years younger with good knees!!