The fabrics that are most suitable for this are silk and cotton or other natural fabrics. Polyester fibres are too slippery and although you can felt with them it is difficult as the wool slips out of the fibre. When felting with fabric you only need one layer of wool and can be as little or as much as you want, it is about the beautiful textures you get and its lightness.
I usually use merino when nuno felting as it is soft fibre so gives it a richness.
Below are some photos of our day .