There are a number of Upstate NY guys I know who deal with these conditions all the time... using nymphs. Unfortunately, most of them use weighted leaders so it becomes a drift-fishing exercise. I'm not contesting the effectiveness of this, it's deadly. I'm just saying my preference is to swing the fly and move the fish to the take. Therein lies the challenge of which you speak.
Thinking back on my own March fishing histories, I have a fairly broad range of memories but can't summarize them into any real singular tactics. Nonetheless, there are some distinct observations I've come to believe heavily in...
1) Native winter fish seem more willing to move for the fly, and act more like steelhead than winter hatchery fish. Although it's true that the higher percentage of fish coming up the river are natives this time of year, I believe the agressive takes and ability to tease them to swung flies (versus bottom bouncing) sets them apart from their hatchery born cousins in a general sense. Therefore, one can fish them in a systematic, almost summer run kind of coverage style with success. This is not to say that increasing hang down times and fishing in the current seams in deep well formed pools won't increase hookups, it will.
2) In clear late winter conditions, I've done well in deep well formed pools with cover and current seams that fish well and hold the line in tension well to maximize the swim time for the fly. The Green River from Flaming Geyser down would be great in these conditions, I used to drift down to the Soos Crk take out with my Bucs Bag pontoon boat. There were always plenty of fish in the pools, and if I had time to stop upriver and fish down to the holding fish I could a put on on the line with fairly consistent results. If the water is skinny you'll have to be cautious to set up before good pools, and good pools don't seem to show their potential until you float over them and flush a pod of steelhead out of them as you go. Unless others are drifting it, you won't see many others on the whole run - and there are big natives in the stretch that are often overlooked.
I had a 7 hookup day (4 landed) pocket fishing with nymphs and small prawn flies on the Tolt one unforgettable March afternoon. The biggest was maybe 7-8 pounds, but in those small river dynamics it was a day I won't soon forget. The water was low and clear, and all of the fish were in dark blue pools where the bottom could not be seen. Don't even know if it's open anymore in March.
I have had a 4 fish March day on the Elwha as well, two out of the first braid below the salmon hatchery, on at the apple orchard and another in the rapids above it. Two chrome, two slightly rose-blushed bucks - all on the black rat.
There are a ton of hatchery fish in the Palmer pool of the upper green if you wanted to test any theories. The Headworks stretch of the Green as well, low water is better for the head of the lower pool. The reason they close the Auburn stretch in mid-month is because the river still gets a return of BIG natives who are willing takers. The year they kept it open until Easter I landed 17 fish in 11 consecutive days. The biggest was a 16 pound hen just down from the Auburn golf course at 2pm in sunshine. I took a drive after Easter dinner to see the river, and found my neighbor and his father-in-law in their Easter clothes & hip waders fishing together! They never kept it open that long since that year.
Now that any chance of a summarized reply is gone, I just wanted to say that I am envious of you who are able to try for native steelhead this time of year. The fun is unraveling the mystery over a lifetime on the river.