Find you a piece of drywall or wood or something to practice on, thin some drywall joint compound so that you can work with it.
It could of been made by crumpled newspaper, or ruffeld plastic stapled to a piece of wood, i would also bunch a rag up and see how close that gets. You will just have to experiment a little as to what comes the closest.
Hard for me to say what they may have originaly used. Someone may have a better idea than me since wall texture does not get done a whole lot around me.