The answer is kinda late, but I'll try nonetheless :)
1. Assign a fabric shader to your geo for the underlying fabric
2. Copy the geo and assign a volume shader to it
3. Put a displacement modifier on the copied geo and assign a noise texture to it that replicates the texture of the fluffy part
4. Play with noise size, displacement height and volume scattering/absorption until it looks right. (I am using the wrong noise obviously...)
