I just used a gallon ice cream tub and added hot water to the powdered rit dye and then added a cup or so of vinegar, then added the feathers and stirred it for 10 minutes or so.
Then I filled a big coffee can up with water and set it on top of the feathers to keep them submerged and came back the next day and poured the liquid into a milk jug.
Rinsed the feathers in cold water untill the water ran clear and then I spread them out to dry.
Make sure they are really dry before you start grinding them unless you did that ahead of dying them. A microwave oven can speed the drying process up considerably but better ask the wife first or wait till shes gone.
Trap