Antibiotic ointment, aka Neosporin (preferably without pain reliever in it), would be the best product to use because it lasts the longest without needing to be reapplied or hardening the membrane. Apply gently with a q-tip being careful not to rupture any blood vessels and avoid the pip area/bill. This will make the membrane translucent so you will also be able to see better once all of the blood vessels are absorbed.
It does not appear to be shrink wrapped yet. The membrane is a healthy white color and appears pliable. It will start to darken and stiffen as it dries from being exposed to air.
The duckling needs to be kept warm but I would be concerned about putting it back under the broody now that the delicate membrane is exposed. Do you have an incubator that you can put it in while it finishes absorbing the blood vessels and yolk sac?
Good luck with the little one!