To each his own. Just the method taught to me. The BB's give weight and stability to the egg. I scrape the edges of the inside of the egg clear of membrane as the membrane will dry out later and take the lining loose. Using the drape stick, or a ceramic needle tool, I start tucking the fabric into place moving the material into folds and gathers.
Small clothespins hold it all in place while it dries.
I do not turn the edge of the fabric under. I cover the raw edges with trim.