The 180 is not required or probably even necessary. I would do it just to make the scratches a little shallower, but that is just me. Just a quick scuff or light blocking. After epoxy, I wait at least overnight before 2K, (24 hrs or more is ideal) but you have up to 7 days before it needs to be scuffed and more epoxy applied. If you do a light blocking it will show any spots that may need more filler, like a low spot or pinholes. Much better to fix it before you spray 2K.