Something that I was doing in my feather grinding was when I got matted feathers, especially primary, before splitting, take and put them in some warm water with just a drop or two of dawn dishwashing liquid. Move them around to get them good and wet and clean. Grab the feathers by the end of the quill and shake off what water you can, and then put them in the dryer. I used high heat and in about 10 minutes they would be dry and stand up just like a new feather. You just have to watch the feather quills getting into the vent hole of the dryer, but that has been minimal at best for me. Feathers come out looking like brand new and clean.