Well you can make a master (sculpt) from a lot of things. Some people like to use wood (MDF or balsa), others use water based clay, and others use oil based clay. Different clays work well for different things, but I prefer using oil based clay for most things. Chavant NSP is a great clay oil to use, and WED clay is a great water based clay.
Any mold making silicone will get you by. I prefer products from Smooth-On
. They make a silicone called OOMOO that is very easy to use. Once you make a mold you can cast most types of resins and epoxies.
Some people skip these steps and build their props one at a time using aluminum or copper etc.. I have seen a lot of Ribbon Devices made from scratch like this. In fact, the first Ribbon Device that I made was made from scratch. One day I might write about it ...