I used Rit dye successfully on some. Just follow the directions. I also had some I never got fully fluffed out, too. Most folks want bright feathers they can see good as the arrow hits the game.
The best thing to dye feathers with is dye. Sorry man, I had to. I did some turkey feathers on arrows for my wife. They turned out really well. I used packs of kool-aid. I'll send you pictures from my phone.
Use a little vinegar with the rizt dye. It helps to set the dye and keeps the colors from fading. Wild turkey feathers are harder to dye so let them set in the dye longer than a farm raised bird.