And, HERE'S the video that taught me to crochet a provisional CO.
But, that wont work for REAL double-knitting. The one above works for FAKE double-knitting, which is what Im calling it when you knit the same hat in opposite directions from the same prov CO and then shove one hat inside the other.
REALY doube-knitting requires that you CO double the number of required sts (using your favorite CO method....I used long-tail) in one color, and then in the next row, start knitting a st with one color and purling a st with another color. This technique automatically forms a double fabric. If you want to add a reversible design, you just switch the colors around for the design. Amy's video shows you that part.