I used to fish the upper reaches of Walnut. The shale underneath the area is very, very soft. That's why you won't really see many rocks that aren't glacially deposited granite from Canada. Why is this important? Because high water can create/erode out substantial features in one good flood, and this happened at lower Walnut. It used to have more of a falls that the fish could jump. After a big rain, it eroded into a chute that they can only get over in the highest of water. So , unfortunately, many miles of water is now almost devoid of fish. Otherwise, I could tell you where to go up here. To get much space to fish, you have to go to Elk, pretty much. 20 mile is really condensed. 16 mile has, what, a mile of fishing till the big falls? Everything else is a smaller stream with even less water until upstream migration is halted.
I use sucker spawn and I've never wanted for another fly. I use some yarn eggs, but not much. Pale yellow angora yarn sucker spawn on sz. 14 short heavy pupa hooks is my go-to. Good gap and strong wire. Pale pink. Darker pink for dirtier water. Oddly, I'm told chartruse is good for the muddiest of water, but I don't fish in those conditions.
for equipment, I find that I use a boringly simple set-up with no regrets. We try to control things with what we use or do, but mostly steelhead are off and hard to catch. When fishing is good, it's good for most everyone. The magic comes from Ma' nature, not you or your stuff. I use a 9 ft. 6 wt. RPL with not one regret in the world. A 9ft. 6" would be better, but I'm not buying another rod just for that. The biggest steelhead stream is not as big as lower Spring or the Little J. or Penns. Not many people use specialty rods there.
I don't think I've ever caught a steelhead on anything besides 4 X tippet. Really, K.I.S.S. Tiny details will count for naught compared to what the water conditions are and how the steelhead act.
And FIGHT the FISH! Use the rod butt. Fight low and off to the side and down. When they are done acting crazy, get them in and get them back.
Syl