Kyle,
Salmon fishing in the Skook is a bad idea, unless you like catching boots - dark fish well beyond table quality. Serious salmon fishing is done much further downstream, in the Chehalis, mostly downstream of Porter, or the Satsop even.
The timing of the steelhead run is variable, but generally it's a late winter run, peaking in April. But fresh steelhead can appear anytime beginning around mid-January, just don't count on it. It's a lot like many terminal area hatchery blood hole fisheries: populated by littering knuckledraggers who don't appreciate the functional difference between snagging and fair hooking a fish. And for the most part, it's not very good fly water, not saying you can't fly fish it, but generally speaking, other rivers are better choices.
Sg