I think the effectiveness of cloth strops depends on two factors. The inhernt smoothness of the material itself and that of how it is woven. I have va NOS Vintage Silk strop that is quite slick but has a very textured weave which makes up for the inherent smoothness of silk. I am sure many of the cloth materials could benifit from a bit of roughing too in order to raise a napp on the surface, just like leather does.

Tony