Just possibly useful info
I fished Skagit Dollys a bunch back in 78-82 when I was working for SCL out of New Halem. Rockport was "Lower Skagit" to us locals. In those times, we didn't know that there was such a thing as bull trout, or the slight possibility of there being Bull Trout mixed in with Dollys below Gorge Dam. And since the Dollys were obviously abundant and eating salmon fry and eggs, they were generally regarded with distain, even by the wardens and "Staters", folks from the WDG. It was generally considered a good thing to thin them out. Some folks caught massive Dollys in Ross Lake and I think there's a higher likelihood that some of those were Bull Trout.
Their fish is paler and softer than other game fish, so the taste was a little disappointing. Much less appealing than their relatives the Brookies. And the fight was much less exciting than a steelhead, but sometimes the large size compensated.
Some years earlier, I found myself in SE Alaska where the locals had much less respect for Dollys. They generally would heave them up into the bushes or wack them over the head and throw them overboard.
I was called on to put on a wet suit and snorkeling gear to rescue some equipment that got fouled in a few feet of water near the gravel pits below Goodel Creek. It was December and the chum were spawning everywhere. But I was amazed to see lots of Dollys, some as big as chums, hanging right below the redds, ready to pick up any lose eggs. They were so big, I was a bit worried they might take a chunk out of me. After seeing all those big Dollys, I was one of the few locals who targeting Dollys because I found that when the chum were spawning the "hatch" was on. We were all hardware chuckers up there, at least for the river fish, and it never occurred to me to try a fly. I threw red and white or red and brass steelie and other spoons into the spawning bed tailouts. Hooking chum in the tail or the back was a waste of time and money, because it would take half a hour to get the spawnout to shore and the spoons cost $1.85 each so I'd do all I could to get the spoon back. We'd take the trebles off the spoons and put on a single siwash hook rigged to point up. Didn't try eggs, but I wonder if an egg pattern fly would work. I also wonder if you might find Dollys behind spawning pinks would also be good too.