I know exactly what you mean.
I would go ahead and close the shoulder seams using the 3-needle bind off, too!
Then, begin picking up the neckline stitches AT A SHOULDER SEAM location. Using a circular needle (prolly a 16" will do)...begin to knit in the round, marking the beginning of the round with a stitch marker.
When the neckline is satisfactory, begin the bind-off round at the stitch marker.
Same principle for the trim on the armholes.
Be very fastidious on what you do with that last bind-off stitch. After you cut the yarn, and thread it back through the last remaining stitch...careful how much you cinch it up...careful how you work the tail into the underside. You don't want the end of the bind off to look irregular.
I'm sure you know what I mean.