If you are attending the convention, I would go to the artist table first thing to secure a spot on the artist sketch list. After you have put your name on the list, then let the artist know that you will be back with the book after you get help removing it from the slab by either CGC or the Facilitator that is at the show. Once the book is removed, a witness will accompany you back to the artist table to drop off the book. When the book is completed, get the witness to go with you to pick it up from the artist.
Use the link @Ron C. provided to figure out what facilitator you might use if CGC isn't going to be there.