I have never made them, but when I make my sculptures, I put some Podge in the mix of flour, water, and bleach.  The Podge is a sealer, as well as a glue.  My sculptures are so rock hard that they can fall off a kitchen table without breaking!!!  There is shiny and matte Podge.  (don't use Gesso).  This method works with paper AND material - ny;on scarves are wonderful ripped up and rearranged into new paterns and shapes.  As for the finishing, I'm not sure what you could use - it isn't normally needed if using stuff indoors - but if you plan to eat off the plates, you might want to add a clear finish of some sort.  I use Varathane Exterior Glossy Varnish for my Garden Sculptures.  Let me know how it goes:  newsharon@cgocable.ca