I did the wax-paper way while constructing CF-FG panel to enforce firewall with. Same method as handgliger's. Quite sucessful.

The beauty of this method is that you have absolute control over the thickness of the pannel, the material used and size.

To keep the total weight down, I tried to squeeze as much as epoxy out for each added layer. The panel is sandwiched between two flat surface (bookshelf panels from Home Depot) and then the weight is added.