what do you mean by -- 'that thick look' ???
high loft batting---or thick/heavy thread???
there are a few high loft batts on the market- they give a quilt a (puffy) look
normally for hand quilting- 1 strand of thread is used- there are lots of weights/sizes of thread-you could use a perle cotton or multiple strand embroidery thread if that is the look you are going for-