I don't swing flies for salmon too much either, but I do know of a few guys who are dialed in to it and do fairly well. In some cooler / rainy years there would be small-medium pushes (and sometimes even major runs) early on, like late August - early September, and before it got crowded you’d get good shots at fishing to some undisturbed fish. With it approaching peak time and the run just starting up this year, the crowds will be much more of an issue, but it can still be done. I would definitely fish the DSR, there is lots of secondary pocket water you can hit, especially if you’re willing to walk - chances are you’ll stumble across a pod somewhere in between the more crowded areas.
Another option is to fish just above town, typically fish will leave the estuary as night falls and sometimes pass through the DSR completely by the next morning, ending up in the area of the Ballpark and on up through the 81 area to the Papermill and above. So if you hit this area at first light you also sometimes have a shot at some relatively undisturbed fish. There have been years when the DSR blanked day in, day out for practically the whole month of September, as the fish ran each night and passed through the area. They were reporting slow fishing while areas upstream did better.
You have the right idea with contrasting colors, I feel this is very important in getting kings to actually strike. I think it has something to do with the fish’s eyesight deteriorating (along with the rest of the fish since it’s no longer feeding as it approaches spawning). In addition to chartreuse and black, I think chartreuse and dark green is even better. If there are cohos running, pink/red or pink/purple works really well in addition to chartreuse. For sunny days switch to the reverse with mostly black or kelly green with a small amount of chartreuse or emerald green.
One other time I really like in the DSR is right around the middle of October, say the week or so after Columbus Day - many years will see a huge run sometime in the first week of October and then it falls off dramatically in the lower river afterwards. That’s when a lot of people start following the run upriver and the pressure falls off in the DSR. But there is usually always one smaller last push of fish that comes in and if you’re there for it you can again have some really good fishing with not as many people around. Plus steelies start showing in better #s around the same time. I avoid the upper river most of the time as the fish are beat up and not nearly as fun to catch. But sometimes there will be high water for a while after a big storm and the fish will charge right up to the top, and if you’re there as the water recedes it can be really good as well.
One other tip – in my experience, fish that have been laying in the estuary for days/weeks and getting pummeled waiting to run the river won’t be nearly as likely to take a fly as fish that get drawn in to the river right from the lake after a storm. So if there’s been just a steady base flow out of the dam for a while but all of a sudden a storm comes through and raises the water, call out sick from work and get up there, that’s your absolute best chance of getting a fish to take on the swing.