If you ever soldered, making a tin mold is like that. You'll have to melt a tin coil onto a sculpt made of wax. Planning a one or two part mold is pretty much like the silicone method but for a two part tin mold, you would set up metal brackets and sockets so you can screw both parts tight during casting. Never done it but I plan to build a cage around my sculpt first with an inch of room then create the mold seperately and try to fit it in, if that gives you ideas.
I saw it done twice, kinda nervous at first seeing hot liquid tin fall on the wax but nothing happens. Its a special wax, forgot the name. The guy heats up this coil and it drips onto the sculpt. It hardens on contact and he forms the mold. . . THEN...you gotta destroy the original sculpt by melting the wax away in order to use the mold to make vinyl copies. Vinyl comes as pellets and you melt them in a pot to get them in liquid form. Pour into your mold and hook it up in your washing machine go at max spin, this spreads the vinyl around the mold. Then you rip it out while hot and let cool. And you have your creation