Step 4: Sanding
Once that was dry, I went forth and sanded. I used a 60 grit first, then progressed to finer and finer grits as I was satisfied with the shape and smoothness of the board.
I spent a lot of time on the edges; I cupped my hand and ran the sand paper the length of the board until I was satisfied with the shape of the rails.
A final note, I found some asymmetries, so I used the planer again, and sanded the area one more time.