I pre-wash everything, which is why I don't buy pre-cuts (at least not often). I did try washing some scraps recently in a mesh bag, and I was not happy with the way they clumped together inside the bag. I think hand washing would be the best way to go, but then the problem is that if they shrink or distort at all they will no longer have their original size and shape, which was presumably what you wanted when you bought them.