My thoughts only. I would make the Holly berries of gumpaste on wire, after taping together you could dip the wire into melted white chocolate and let it set before pushing them into the styrofoam cone. At the same time, if the wire isn’t really touching anything edible I wouldn’t worry about it. You could also make the berries and leaves of fondant or modeling chocolate without wires and attach them with a dab of melted white chocolate so it isn’t seen when the tree is completed. Time consuming holding each berry until the chocolate has set, unless you use a freeze spray. To make the berries shiny you could brush lightly with vegetable oil or a confectioners glaze made of equal parts of vodka and clear corn syrup. It dries shiny without being sticky.
Shirley