Modifying existing props or accessories is a smart way to save time (and probably money) when you’re working on a cosplay project. For example, Instructables user Eldalote used a plain helmet as the base for a dwarven helmet. The base can be metal or plastic. You only need to make few alterations with modeling clay, leather, hot glue, and paint to transform it. He recommends starting with several sketches. He decided to add fake rib embellishments made from the modeling clay:
Take a piece of thermoset clay and start forming some fake ribs. It’s a little tricky, but I’m sure you can make it! I made two same ribs on the sides and then one on the front.
Make a basic shape and then make some holes and shapes into it.
When you are done with shaping just put it in the boiling water. I wasn’t able to take out the clay from helmet easily, so I used a string and slowly cut it from it.
When it’s hard you can adjust it with a knife. Then take your paints and do some paintjob. I used golden spray and then shaded it with acrylic colors.
After that simply glue it with hotglue on the helmet.
Read more at Instructables.