try this stuff....
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82698
this is a complete casting kit...including the mold material, casting resin and mold release.
i have used this stuff and it :cussing: rocks!!
i was shown this product by a train builder, who made his own terrain pieces.
hope this helps.
cheers:beer::beer: