The Rig
The job of this rig is to get your bait down to where the salmon are and allow your herring to spin freely.  The rig itself is fairly simple and consists of:
The Leader - Chinook are not leader shy so you can use a pretty heavy leader.  The pre-tied Owner mooching set-ups I usually use are tied on 30 or 40lb test mono.  For kayak fishing I find a length of 4 to 5 feet works well.  Too short and I believe that the roll of the herring is affected, Too long and netting your fish is next to impossible.
The dropper – A piece of mono approximately 10 to 24 inches long that attaches the weight to the swivel.  Use a dropper line that is lighter than your main line so that if your weight snags, you don’t lose the whole rig.
The Weight – Use enough weight to keep your bait down.  I prefer 4 to 6 ounces of weight.  If the angle of your line is less than 45deg, your weight is probably appropriate.  If the angle is greater than 45deg at normal trolling speed then you probably need to increase your weight.
The Connection - There are lots of different ways to tie these three things together but I find that attaching the dropper to a sliding swivel above the main swivel works best. I like to use a sliding swivel because it reduces the amount of resistance that the fish feels when taking your bait.



Plug cutting
The reason you plug cut a herring is to facilitate a rolling action when it’s pulled thru the water.  A plug cut is a roughly 45deg cut from just behind the head down to the belly, with a bevel.



The Roll
It’s all about the roll.  
If your bait isn’t rolling, it’s not going to get bitten.  
To get a good roll, run the front hook (the hook closest to the swivel) from inside the body cavity (approximately ¼ inch in), out through it’s back, along the spine.  Now, run the trailing hook thru the herring at the lateral line starting at the long side and coming out the short side.
The front hook should be at about the 11:00 o’clock position.  If your bait doesn’t roll when you check it, try adjusting the position of the front hook.  If it still won’t roll, toss it and try again with another bait.




Location, Location, Location
Fish where the fish are.  
If you have a fish finder, look for stretches of river with a depth that’s consistently between 15’ and 30’ deep.  Focus on the insides of corners, the lower ends of islands and areas where wide flats taper on the upstream side.  If you don’t have a fish finder, you can follow the powerboats that are trolling an area.
For new stretches of water I’d suggest checking out the NOAA charts for structure that fits the descriptions above.  http://www.charts.noaa.gov/OnLineViewer/18525.shtml is a good starting point for the Portland area.

Trolling
This is where it all comes together.  
Deploying – To deploy your rig, put your rod in the holder and let out enough line so that the swivel is an inch or two below the surface.  Take a couple of strokes and check your roll.  If the roll looks good, take a couple of hard strokes and hit freespool.  As soon as the weight hits the bottom, crank it up 3 turns.  At this point, your line should be at a 30 to 45deg angle.  
Trolling Speed - You want your herring moving thru the water at between 1 and 2 MPH when trolling.  This means that yak could be moving downstream at 5 MPH, upstream at -1 MPH or anywhere in between.  Keep an eye on the angle of your line.  If you notice it stretching back beyond 45deg, slow your paddling.  If it’s still stretching out, you may need to increase your weight.  
Turning Around – At some point you’ll probably need to turn around and troll back.  You have two choices here, make a really wide turn or reel in and re-deploy once you’ve turned around.  If you try a small radius turn with your rig deployed, chances are it’s going to get twisted and tangled.

Brining Herring
It’s not a must but it helps.  
The basic brine recipe is simply a cup of non-iodized salt to a quart of water.  If you have the time, add the salt to hot tap water and allow it to cool overnight in an open container. (I do this outside on a cold night or in the fridge once the temperature has dropped a bit)  The warm water helps the salt to dissolve completely and the sit time allows some of the chlorine to evaporate.  Once your brine is cold, simply place the whole herring in your brine for 8 to 12 hours in the refrigerator.  

Good Luck and Tight Lines!
-Spot-