Is there such a place as "Collar Island"? There ought to be. I always underestimate the length of time it takes to knit a deep shawl collar. It inevitably feels like forever. The only way for me to get it done is to pull up a good audio book on my phone and stick with it.
Finally, on Day 2, while dinner was in the oven, I finished the casting off (regular casting off in pattern for the buttonbands, and Jeny's Surprisingly Stretchy Bind Off for the collar).
Now only the underarm closure (this method), weaving in, and blocking remain. Look carefully and you'll notice that the lower body has already been blocked while the upper body and most of one sleeve are still a puckered mess. Time to get out the button box to see what might work.