The wax in the original canopy is only to stop the Plaster of Paris from sticking to it. Some people use a layer of food film inside the original to do the same job but there is a risk of "Crease Marks" from the film that you will need to fill and sand out.

For the final one no wax will be required. If you want to be absolutely certain you can seal the "Plug" with furniture varnish. (I use Shellac - the stuff used for French Polishing that is made from dead beetles).