Chris,
There is as many of opinions as there are people on this topic. Fishermans choice, so hopefully enough people pitch in for you to formulate your own recipe to kill nooks with herring.
As far as brine, any commercial bought brine from Bi-mart, or any willy-nilly sporting goods store will work. Ive used the Salmon U's brine, caught fish. Pautzkie's- caught fish. Used Pro-cure's, caught fish.
Common theme, herring was the bait.
I dont think it matters what you bathe your bait in as long as its salty, and toughens the hid a little. Im more interested in a GOOD bait, IE- a herring with as much of the scales on it as possible, to produce a good flash. I prefer to brine them the night before, take them to the river in the brine, and as I take a few out of the container, Ill take a few from a fresh pack and put them in. Whats left at the end of the day gets tossed away, and I start over again.
Next is the motion, the action. I think the movement of your bait is more critical than anything. Your bait could be the most awesome smelling, tasting bait in the world, but if it aint giving the proper dance to excite the fish, it wont matter.
As for size, my personal feeling is the bigger the better. Think Texas. Ive caught fish on greens, blues, purples. I go with greens for spring fish in the Willamette, but fall fish are more aggressive and less shy, they are coming into the rivers with substantially warmer waters. So with a bigger bait, you get a bigger flash, bigger presence in the water column. Ill fish a purple in the fall. Sometimes a blue.