I need a grinding stone, but not sure what I'm looking for. Can you help me?

The main manufactures of rotary tools are dremel (http://www.dremel.com/Pages/default.aspx) and rotozip (http://www.rotozip.com/) the tool that may work best for you is a dremel. there are hundreds of different attachments that can be purchased for the dremel including many different types of grinding stones. dremel offers many different models of rotary tools to suit your needs. Hopefully this information will help guide you to a solution for your project. Good luck!