Some artist preferred rub pastel into the texture of the paper and some don't. When you rub onto paper with multiple colors you created a smooth surface. Sometime you just need to have each stroke shows. The reason I choose velour paper for this demo is because you simply cannot mix colors on velour paper. That's why I think it is a good practice to use this paper for the layering technic.
Please see the video on youtube for the demo.
https://youtu.be/1D2XKNy_Qrs