Loki’s primary weapon in The Avengers was a Chitauri Scepter. It has an elegant design, and Instructables user KyleofAsgard made one using a couple of types of foam (EVA and expanding), silicone, and Plaster of Paris among other materials. He started by scaling the scepter to the right size by using a grid. He then transferred the stencil to cardboard and covered both sides of the new cardboard template with expanding foam (specifics on doing that here). After he cut off the excess foam around the scepter template and shaped it, he covered it with Builder’s Bog:
Builders bog is a very popularly used costume/prop makers material, It takes 2 parts, the bog, and the hardner.
Usually for every golfball sized bit of bog you use, you would squeeze a 25mm line of hardner from the tube to mix with the bog.
What you are going to do here is basically cover your entire foam sculpt of your staff in bog, a really easy way of doing this is to wear latex gloves and use your hands, If you dont have gloves, then usually covering your hands in canola oil will do the trick to stop it sticking.
Make sure that you give your model atleast a 3mm thick coat all the way around ‘minimal’, Ideally if you can make it 4 or 5mm then you will have a stronger finished product after sanding. The cleaner you can put this bog on, the easier detailing will become.
Read more about the rest of the project at Instructables.