Question: How do I smooth the edges of the board ?

  Options: 
 A. Use a sander with 120 grit paper, you might want to use a drill with a sanding attachment for the holes, or you could also sand it by hand.
 B. Use a sandblaster at 120 psi, you might want to use a drill with a sanding attachment for the holes, or you could also sand it by hand.
Answer: A