The lower river is fishable. It's marginal, but improving. I saw a couple of guys chuckin' gear below Horn Rapids today. And it has dropped about 2k cfm over the past week or so. Maybe we will get a shot at them afterall......
It'll happen, just be prepared to lose a few. I've only managed to land 2 on the flyrod but have lost twice that. The worst ass-handing I've ever had in freshwater was from a very fresh springer (just guessing) that was in the high 20's to mid 30's. It almost spooled me running upriver through class III whitewater.
I'm no expert by any means but have learned a few things. For swinging purposes, they will hold in "steelhead" water but typically seem to like somewhat deeper/slower water. Especially if there is some structure in the form of large boulders or ledges. This one ate in pretty classic steelhead water about 4-5' deep where the run was transitioning into a narrow tailout. It was also fairly early in the morning, shaded water, and at the top of a good stretch of rapids. Three factors that seem worth paying attention to with springers.
Given that the odds are already stacked against spring chinook fly fishermen, I for one don't think there's too much shame with "dead drifting" weighted flies. For this I like a full floating line, long leader with a TBH bugger, ESL or similar. Find a known holding pool with a nice chute at the head, and work the seam first thing in the morning. Don't use an indi since these spots typically have a pretty good depth gradient. The fly might start in water only 3' deep and end up in swinging into the pool where it's 15+. Depending on the spot, you might be nymphing, swinging, and end with a hangback on a single cast. All three stand a chance of connecting.