Hi markfrid,
Alaska is a wonderful place to visit or live.
There is great Grayling fishing in Alaska and worth your effort. Not the best fish to eat but OK if you eat them while fresh. We use to carry a frying pan, oil and flower in the canoe when we fished for Grayling. Made a great river side lunch. I lived in the interior and Grayling was the predominant fish.
The best flies depends on your objective. Many people fish Grayling with dry flies. I started dry fly fishing for Grayling but never consistently caught big fish. I later switched to wet fly fishing and had great success with big flies.
Dry Flies: Black Gnat, Griffith's Gnat, Irresistible.
My favorite was the Irresistible with the Griffith's Gnat a close second. Size 12, 14.
I tried a lot of wet flies and eventually stopped dry fly fishing for Grayling as the wet flies were so successful. My best fly for most fish was a small wooly worm that I tied my self. This was a really successful fly. I used gray Chenille as the body, black thread head and a red wool butt with a natural grizzly hackle palmered over the body. Size 12/14. I did tie a few strands of Peacock Herl pulled over the back. The dark herl back contrasted with the gray body. I almost forgot the most important item. I wrapped the hook with lead wire and glued it before wrapping the body.
My other Grayling killer was a Burlap Fly tied as a streamer. It had the burlap body that I picked out a lot after the fly was completed. Gave good definition to the body. Grizzly wing and tail. I don't remember what size hook but it may have been a size 10 or 8 long shank streamer hook. It was a big bite for Grayling but caught big Grayling. Also wrapped the hook with lead wire.
The secret to wet fly fishing for Grayling is movement. I used a wet tip fly line and I think the tip was about 10' long. Grayling like pools with moving water into the pool. they sit at the edges of the moving water waiting for food to be washed down to them. Even in big rivers I looked for moving/calm water. The trick was to let the fly sink and then do a tip lift that pulled the fly up a few inches and then settle back down. Normally the fish is watching that fly and when it rises they can't stand it. The bite almost always came on the tip lift. I never had good luck with wet fly fishing for Grayling with a dead drift. They wanted that movement.
Frank
