I haven’t used rough-finished watercolor paper in a while. I remember that I enjoyed working with this texture. To increase the irregularities of the surface, I obtained a spray bottle and some pretzel salt. I applied the pigments as usual,  applied the salt and soaked the paper with my nebulizer.

Watercolor Nebula
12″x9″ 140# Rough Watercolor Block

Voilá, a nebula!