You can try Jack Cook at Irishangler.com. Don't know if he's a sponsor (sorry) but he's a good guy and knows the river. I will say you NEED a guide, at least on day 1. The fly water can look a little odd. Lots of pots and small runs to fish in between the classic bars and you need experienced eyes to point all that out. Access is a bit tough too.
I will say that one of the most beautiful places I've ever been, if not THE most, is the Sauk River valley below Darrington. The river is just 'brawling' which to me epitomizes the Steelhead river. Wade with a stick for sure.
The Sauk 'bar' on the Skagit is below the campground in Rockport and I hear there's a trail. I fished it on a float, nice BIG run.