I went to school in Chico and spent more time on the Feather than in class. Most guys egg or nymph as you say. I quit the Feather several years ago, because it really became your stereotypical combat fishery. The gear fishermen were, generally, better mannered than the fly guys, which might tell you everything you need to know. Oh, and the wildlife preserve where most people park is patrolled 24/7 by junkies from Oroville. Nothing short of the wild, wild west on that account. Leave NOTHING in your car, not a shirt on the seat, nothing.
That said, some of my fondest steelhead memories took place on the Feather. By Thanksgiving most of the salmon are dead and gone, so the steelhead are a little less focused on eggs. They do respond well to small mayfly and bead head caddis pupae (Pupa versions are popular), like you said. These fish stay in the riffles and around salmon redds long after the salmon die. Hopefully there were enough salmon this year to slow the steelhead down. If you want to swing and don't care what's tied on the business end, then you'll catch more fish with the same stuff you'd otherwise dead drift. A high density tip and properly aligned cast will catch plenty of fish.
These little hatchery footballs (2-5 lbs average, despite what any local shop "expert" might tell you), get a little more dour as the season wanes, and it always seemed harder to get bit with anything but egg patterns and small nymphs/pupae during and after the salmon spawn. But I had quite good luck swinging shiny little fry patterns late November on. Did go against the grain enough with leaches and sunk muddlers but never had much success. An old pattern I success with was a version of the old Horner's shrimp with bead chain eyes. I swung it with short, decisive strips off the dangle. Super easy recipe:
#6-8 standard down egg nymph hook, not long shank
one bunch of brown bucktail, tied at bend, leaving a tail roughly as long or a little longer than the shank; keep front half to fold over as shell case at the end
tie on a soft natural brown saddle to wrap forward
tie on some daimond braid or any tinsel and wrap to the head
wrap/palmer your saddle forward to the head
guide saddle fibers down and back with fingers, then stretch your bucktail over the back and tie down at head; I frequently left a little nub (elk hair caddis style) to create more turbulence.
put a little head cement over the back/shell case and call it good
**the buck tail frays/breaks pretty fast as you catch fish. But it's such a fast, effective tie I never cared. Forgot about the bead-chain eyes. Do that first. I know, it's not the most aesthetically appealing fly, but there's something about it on the Feather. Swing it.
Don't be deterred by the spill over from "O" town. There are bigger fish too, just not many. My two best were an 8 and 12 pounder. The smaller average fish are usually great fighters and jump a lot. Go for it!!
My brother still lives in our home town Chico, California. He normally comes up to central oregon for steelhead fishing with me each fall but he has ben to busy with work to make it. I will be there for Thanksgiving this year. We would have only one day to fish so the better nor cal options like the Trinity would be out I think as we would need to keep it within an hours drive.
I grew up in Chico and remember the millions of fish at the hatchery at Feather River... I have searched and searched online and come up with a little info on the Feather River and the only technique's recommended are nymphing eggs behind salmon and sounds like mayfly nymphs work too. My bro will nymph I will want to swing... I would ASSUME it would work fine but wanted to know if anyone had any insight to this off the beaten path likely mediocre river?