Oddly enough, I’m not 100% sure this is required any longer. Today when I rolled back from 11.2, to 11.1b5, my watch synced all on its own without having to be removed or re-paired to my iPhone.
Every other time that I have rolled back from an iOS update, I had to reset the watch and restore from a backup. This time it just worked.
Edit: this was on a S3 LTE, so your experience may differ.