Jim,
I think that the term "lost foam casting" is what threw us. Usually that refers to making a foam part and either putting plaster around or making a sand mold. Then when you pour your metal in it burns the foam away.
What you are talking about is to make a foam part then glass it and loosing the foam inside to form a new mold. It might work. Once you loose the foam the inside surface is somewhat rough and hard to put parting agent onto.
A better way is to make the foam part and put resin on to firm up the surface and make it non-porus. Sand it really smooth. Apply parting agent and wax. Then make a new mold from that. Your inside surface of the mold will be as smooth as the part you started with.
Try this link:
Here
Good Luck,
Chris