No problem posting more shoulders cast off etc. There are all sorts of variations. When you bind off, you'll knit 2sts and then begin to count the sts lifted over and off the needle. When you've lifted over 10sts, you'll be left with one st on the righthand needle. here's a video for casting off.
You're basically working the shoulders one at a time with 28sts center sts on a holder for the neck. When it says to join c2, you'll have to join a new end of the color you're using and then work the second shoulder. It may help to write out the decreases for the neck and shoulder bind offs on a drawing and then check them off as you do them. It helps make sense of "at the same time" directions.