I am now dealing with these on my ZR2. A area that once was taken care of with hyperdressing 1:4 on the normal plastic ones. Well, I have been using 3D Yellow degreaser 1:4 on the fabric ones. I spray them with the 3D and let them dwell a bit. Then hit them with a strong jet of water. So far this has been working. Needless to say, I have a lot of hyperdressing going nowhere. But I will find other uses for it.
UPDATE: I have now read other posts that some members are actually spraying the hyperdressing on the felt liners after cleaning. I have not tried this yet. And don't know if their would be any benefit of doing so?