Thanks so much for all your comments and suggestions regarding the blanket stitch on the Posh Pillowcase. I tried almost all your suggestions. Here's my take:
Skip Stitch Blade: Ummm. No thanks. Some people love this blade. My insane battle with perfection would not allow me to embrace this blade. I did not like the holes it left in the pillowcase. In fact, I have a pillowcase that will never leave the house. It will probably be repurposed into wallets or some such thing.
Sharp Hook: See Skip Blade above.
Single Length of Yarn (photo above): This was a viable option. The yarn did not tangle and was easy to pull through the fabric even when it was a long length. A single length of yarn also seems to provide an adequate foundation. I personally do not like the look of the single length as well as the doubled yarn.
So what is my new solution? Sew the blanket stitch with a shorter-length doubled yarn in two separate pieces. Start your stitch as you normally would in the "pocket" by the seam. Sew around to the other seam ending in the "pocket". Remove your needle. Thread the second piece of yarn. Join your second length of doubled yarn to the first. Continue around the pillow case and join to your original yarn. You end up with two knots instead of one. I'm okay with that. This is probably only make sense to those of you that have tried the tutorial. So sorry if you are reading and wondering.
Now if your head is hurting from reading my drivel and you've decided to NEVER EVER EVER try to make a Posh Pillowcase, I have good news. I just listed ten new pillowcase in the shop. Woo Hoo!
Happy day,
Cassie