I have a soft spot for roos. Matter of fact I'm meeting someone to pick up yet another one today. His feathers are different, so that's nice.
I've been buying feather for decades and I can tell you that what I find in my yard and coops are better than most that I have paid a lot for.
What I do is walk around while I'm out feeding and watering or cleaning and I keep my eyes open for nice feathers. Even if they are dirty I can clean them. I used to steam them and shape them one at a time, but I can tell you how I do it and maybe someone has a better way and can share.
I have ziplock bags that I carry with me. Find those feathers and grab them up and move on to do something else. I keep them in a bag for a week. My reason being that I do dust my birds and I check them and know they are pest free, but why take a chance. Anything that could be on them will sufficate after a week or more. Oh and most times it's longer. I'd be working feathers till my fingers fell off.
I shampoo them twice.
First shampoo is with a cheap, maybe $.99 store dog shampoo.
Dawn dishwasher detergent also works great.
Second shampoo I use a human type shampoo.
Make sure you rinse them really well.
I forgot to mention that I either bind them or stitch them together at the quiills. Holds them in place and you can clean more at one time and dry them.
I use a blow dryer and fluff them out to their nature state.
I like natural bends in most feathers, But I also make feather fans and dance regalia, so I'm been very picky over the years, but hey, I'm getting older.
I use a peice of cotton material, a pillow case, cheescloth or whatever and lay the feathers on one layer and cover with another and steam them flat with an iron. I used to do this one feather at a time over a pot of boiling water and still do if it is for something that must be done this way.
While they are still slightly moist from the steam, you can re-shape them.
It's that easy.
I've made so many things with feathers over the years and I always tell people that if they get dirty or dingy to wash and blow dry them. If they aren't torn up and damaged they will last for years and years.
If you remove them from a butchered bird, do not soak. The feathers will be a horrible mess to clean. Just yank.
No exaggeration, I probably collected a couple thousand feathers in the past week. And I just got 3 Black Sumatras and found my first hackle feather. Gorgeous! Can't wait to find more so I can make myself some earrings and a hair clip.
BTW you can dye them also. I use food coloring and then set them with vinegar. The smell goes away and they smell really clean. You can also use fabric dyes.