I did a light sand blast like that a few years back. The right grain orientation makes a big difference. The soft appearance of driftwood is really quite attractive. You're off to a great start. If you don't already have a sand blast cabinet, I recommend one (about $100 @ Harbor Fright). They make the job a lot cleaner and automatically recycle the abrasive. I used play box sand and it worked well. The courser cement mixing sand, not so much. Adding a pressure regulator really gives you a lot of control so you can adjust the impact of the abrasive to be lighter or heavier based on how the grain in that area is responding. Keep posting pics and good work.