Yah, the opacity gives it away. I don't think there is much or maybe no control over the particular app I used to draw it with. It's done with an ipad in zenbrush2, which mimics the brushes really well but there isn't much control over canvas size or anything, maybe none at all. i'm not really sure even. I normally use different programs that are more diverse.
I actually went looking through my art folders to see if I could find my real one done with an actual brush like I was saying but I guess I never saved it digitally. It's at another house, or buried in a box somewhere here. My favorite piece I ever did with one of those brushes is done with a real one, and I wanted to share it after hearing your question. But just too much work to try and look for it.