I used to have consistent luck with tidewater kings in the golf course hole on the Green, particularly the nursery hole. I've also caught them at various pools downriver down to southcenter, and some upriver as far up as Palmer but the ones that really grab the fly are in the end of tidewater.
There are a few rules... you'll get 99% of the strikes at first light and dusk. The odds are against in mid-day.
I have had success with a number of flies but most of them are orange although I have had them take the bunny rat in black several times as well.
Choose a pattern that is animate and a position that lets you swim it in the current. Hang downs in their lair works best, but I've had them rip my arm off on the swing before as well. It's a matter of swimming the fly in their zone when they are willing to eat, which is a fairly limited time slot in most cases.
To my surprise, I've hooked them on floating line with a long leader and sparse flies as long as the swing is s-l-o-w and the fly gets some depth. I also use light tips to pull the bunny rat down and allow me to swim the fly in the tailout longer, throwing mends to swing the fly left and right.
This is not a fishery for light or cheap tackle. They will bust you up badly. A 10wt is recommended, and that drag better be perfect.
Jacks tend to be more willing, and they are no slouch on the flyrod either, but when you get the 30 pounder in a current...
When the roe and bobber crew are killing them on the tidewater, you know they are in a taking mood. Go there as early as possible and get a good spot, some only require a good roll cast to set up the fly.
One of my successful flies was an estaz bodied wet fly with a marabou wing, hot pink tail and yellow collar hackle. The marabou was a shrimp pink color, but kind of dull. Another was a bunny rat tied in orange, orange dyed deerhair and bunny strips from Morning Hatch (who has great material colors) in Tacoma.
I think the fly matters less than the presentation and the fish's willingness to eat. Luckily I lived only a few miles away so could go before and after work everyday, increasing the chance that I would get them on the bite. When they were, they can be very aggressive.
You know they are there, it's just a matter of playing the game the way they want it.
I can't stress how strong they are, you had better be armed for battle when you hook one!