that's-- I open the texture on photoshop, copy that texture layer, and paste it on the drawing. then you can choose the texture layer mode to multiply, overlay, soft light, etc . is it something like that? 8D
Just one question: why you draw so pretty? Like always I like the color, the pose and everything. I like the ocean by the way but if you like to make it more real maybe draw some waves. Your style is recognizable, which is really a good thing. Keep on!