Mooching is the classic chinook fishing method. I am with Speyguy on whole herring, I haven't seen many herring swimming around without a head. My setup of choice, a 10 foot rod, single action reel, 8 feet of limp leader to a small swivel, and a 2 foot stiff leader to the hooks. Use a sliding weight on the mainline, the size is what it takes to get to the bottom for chinook. Dogfish (and coho) will grab anything including the heads from the cut plugs. Mature chinook are like catfish, they may feed at the surface at night but most of the time they like to hang out on the bottom and let the food come to them. Drop offs, holes on the bottom, even big rocks where tides concentrate the bait are favorites hangouts. As other people have said 60 feet and deeper is good as long as there is some structure nearby that concentrates the bait. Not recently, but for many years we fished at Port Angeles, the two weeks around August 1. There were many good chinook fishermen there, it took a few years to learn, watching them, getting to know them and talking to them but it was time well spent. 8 years in a row my wife got a 30 pound plus on August 1st. Another hint don't stop at 150 feet. Many of the chinook we caught were at 200 to 300 feet right on the bottom. We used to call downrigger fishermen terrorist because it seemed anytime you had a big chinook on they would troll over to see what was happening and cut it off. We fish downriggers most of the time now in area 9/10 but make a special effort to avoid the terrorist label.