This is the Roc-Lon 100% cotton muslin that I recommend using to make my dolls. It has a fine, smooth surface for paint, embroidery, glue... any embellishment. At a 180 thread count, it has a good amount of stretch, and that can make a big difference in the ease of turning fingers and miniature dolls. It's readily available, but you can buy it here, too!

Unbleached muslin - 1 yard cut
Price: $2.99