Im making a beer mug and have covered in Modelling chocolate. Is there any way I can make it shiny so it looks like glass?

You can try to use a mixture of equal parts corn syrup and a clear spirit like vodka. Mix the corn syrup and vodka together until incorporated and brush on the modelling chocolate. I use this to make fondant chocolate shiny and it works great! The vodka evaporates so there is no taste and when it dries, it is not sticky. Hope that helps.