This is a post I did on another forum with almost the same question...thought some of it may apply
Remember, winter steelhead are typically not hungry, they are territorial because they just came into this cramped river after swimming around in the wide open ocean AND they're full of love hormones AND they are competing for space...these big flowy flies we use are invaders (that's why they're called Intruders) in their space and they lash out to protect their little personal bubble....
Summer steelhead are different, they come into the river in spring/summer sexually immature and actively hunt and eat all summer before joining the winter crowd to spawn
PATTERNS
If I fished intruders, that's ALL I would fish in every color/shape variation possible. They're too hard to cast on my 7 wt switch. One of my buddies is a rabid INTRUDER ONLY fisherman and banks several fish every year. He has multiple large boxes full of flies! And, he fishes/ties/loses flies more than we even think about it.
Another buddy is a wooly bugger freak...winter, summer and salmon season...tie a bright dubbing ball on the front of a black or purple sz 2 bugger...good one
Try spraying your flies with a UV enhancer or marking them with a permanent blacklight pen
*I may have let the cat out on this one...
Secret of success? Intruders are big, colorful, and have lots if boogie!!! Upsize for low visibility, downsize for high visibility...Bright day, bright fly/dark day, dark fly...basic but important
That said, I've found success with bright/dark bunny leeches (sz 2, 7/64" beadhead, cactus chenille body, zonker strip wing), Early/late season, thread on a soft 6mm bead in front of a black bunny leech and hang on!
Clouser Minnows...pink/white, red/white, purple/white (sz 2-1/0, 3" long, longish shank hook or shank/trailer with heavy eyes)
Large (sz 2-1/0) Matuka style flies in bright and dark colors tied with feathers and/or zonker strips...
All with plenty of color contrast and movement.
Classics (in sz 2-1/0, heavy irons) like Winter's Hope, Green Butt Skunk, Purple Peril, Street Walker, etc. have and do produce. One trouble with the classic flies is that they perform best when unweighted and are hard to get them down to the fish. I have weighted them with beadheads and wire where legal with some success but sink tips/poly leaders are king.
COLORS
Think about adding some flash, hot pink or cerise, chartreuse and kingfisher blue into your bright day rotation and do some black/purple, black/blue, solid black patterns for our typical PNW winter days ... for your hackle prop use a hot spot (bright bead, dubbing ball, cactus chenille, etc.) for added contrast. Color contrast within your pattern is key. Also, colors like red and orange disappear at the shallowist depths...blues, purples and hot pinks continue to reflect light up to 12 feet deep in our steelhead green water even on cloudy days.
MATERIALS
Movement, flowiness and sparseness are key!!
If you keep it cheap like I do (I lose lots of flies) use materials like marabou, schlappen, rabbit zonker strips (1/8" move best), sili legs and whole, thin dry fly hackle feathers (I've used decorative hair feathers too, decent replacements for rhea fibers), cactus chenille, arctic fox tail, finn racoon, bucktail, flashabou, dubbing, hard and soft beads, dumbell eyes, weight wire, etc.
Winter steelheading can be compared to gambling...don't take any flies to the river that you're not willing to lose. By that, I mean you should be fishing within a foot of the bottom and snagging logs, rocks, grass, etc. is often the result. That means lost gear...There are multiple ways to accomplish depth... weighting your fly, using sink tips/ploy leaders or tying flies on heavy wire hooks and fishing on long mono leaders.
Sorry for the long post...Hope you find some of it useful!!
PM me and I can offer more info or I can mine my buddies for info
Cheers!!!