It sounds to me like you will first need a white topper fabric so your main fabric doesn't show through the unstitched portions of your embroidery design. Then if you decide to use a fluffy white fabric like minky you'll need a tear away topper so your stitches won't sink and disappear into the minky. There are several things you could use as a topper. There's one that melts away with your iron, a tear away type and a wash away. You might want to try the saran wrap like suggested above on your test run over the minky if you don't have these topper stabilizers on hand.