Step 1: Rough mill the 2x4s
First, on the miter saw, I squared off one end of each 2x4 and then cut them to 6' They were roughly 3 3/4" thick. I used the table saw to rip 3/16" to get each plank to 3 9/16". (Later, I will take off another 1/16 using the planer.) After all that was done, I spent some quality time with the orbital sander. I first hit each one with 120 grit and then again with 220. The main goal was to clean the surface and maybe get some of the splinters out. In hindsight, I should've cut them a little longer than my desired finish length, but everything worked out.