I love your brush strokes! Well the picture is awesome too..... Do you mind are you using traditional oil or digital? The sand reminds me off the grow a rock kits I had as a child it was called Magic Rocks. I love the soft image and brush strokes it reminds me of etherial sand.
It's completely digital. I use custom brushes. they can be found here: fav.me/d6souir
It's a huge package of brushes I found on the net yet I only use maybe 6-7 different brushes at a time. At a later date I will have to sort them out lol. I am also uploading a speed paint via youtube about this, and later tutorial.