I made a video on how to make silicone molds out of small objects to use with polymer clay.
I use Siligum, a two part silicone compound that dries quickly and makes a flexible mold. This material makes a clear impression and captures every detail of the object being molded. You can use the mold to make duplicates of the objects in polymer clay, metal clay or resin. I focus on the difference between molding a thin or a thicker object and how to fix a hole in your mold.
I hope it's helpful.