Although I have no pictures, the feather butts will be free in their feather tracts, the quills will be sharp, and the coloration of the feather on the opposite side of the skin will be showing through.
As far as degreasing goes, it will be the argument of the Century as to whether or not soaking in Mineral Spirits, White Gas, Gas, etc. etc. will actually degrease a bird. In my opinion, solvents are only that, due to their specific gravity, they will aid in the removal of particles, because of their densities in comparison to one another. duck fat is an oil, and these solvents are (nine times out of ten) oil based, so removing oil? I'm not so sure about that. I do use Odorless Mineral Spirits after I wash in soapy water, to help the drying process, and I do have a bit of colored water in the bottom of the bath, but that probably means that I didn't wash properly, or enough times. I like to flesh, wash in warm water with a degreaser that I bought commercially (used in oil removal in huge vats) PH is 8.5 nearly neutral, but with warm water (also a different specific gravity than oil) along with a toothbrush, and a soapy solution, removes the majority of fat. The solution of crap in the bottom of the solvent bath is more than likely fat, soap and water that was improperly removed during the washing and rinsing process. In other words more is coming out of the feathers than is coming from an improperly fleshed skin. Please don't feel you can take a shortcut in fleshing because you THINK you can remove the fat during the solvent bath. I think that fleshing, washing, and rinsing are all equal in their necessity in cleaning the feathers and skin of a bird. Rinsing is probably the one that is overlooked the most. I seen on another website, of a bucket that had a hose connection on the bottom, and when the water filterd up and around the bird's skin, it would remove all the fat and soap, because fat floats on water. When the water was completely clear, then and only then was the skin completely cleaned. (Thanks Wingman)