Truffle help?

I thought I would try my hand at making truffles this holiday season, using FC March 2008, pg 70. I made it past the shaping and refridgerating step and have a question on the coating with melted chocolate, which is next. The article reminds you that you have to work quickly to not have the melted chocolate harden before you coat the truffles in cacao powder. So, I used a double boiler to melt the chocolate. When coating the truffles it gets to be a Mess, with the truffles melting. Is my melted chocolate too hot? As the mixture cooled a little it seemed work a little better. Is there an optimum temperature for the melted chocolate?