The next step is to get the belt sander out and get the bulk of the glue off with a coarse grit (I used 80). I kept going until each section would sit flat and feed through the table saw without rocking. Then I skimmed the edges with the table saw until they were straight and square.

Then more glue, some clamps, and a few bonus solid straight edges making sure things weren't bowing out of shape.

Once that's thoroughly dry, back to the belt sander. This time I kept going until all the glue was gone from the faces. Then switched to 120grit to get any grooves and the worst of the scratches out (caused by the coarser grit).

I gave it a quick going over with the random orbit sander to show up missed patches, and jumped back and forth between the belt and random orbit sander until I was satisfied things were even and the deep scratches gone.