I'm afraid you've lost me a little now. Can you post a picture or two of exactly what it is you're trying to cast.
There are various materials you can use for one-shot moulds. I've used candle wax for making small items, which will hold for a few pulls, then it begins to burn out, as the heat from the resins curing process begins to effect the surface of the wax mould (more of an issue with polyester and polyurethane than epoxy resin). I just melt the wax back down, repour the mould and off you go again. As it's wax, it is self-releasing from any resin, so no prep needed on the master or the tool for subsequent castings.
If the object has any undercuts, then this method won't work, as the original item will lock in, and the wax has no flexibility to pull clear. You can get a hot melt vinyl material called vinylmold. This is a material that can be heated up in an oven or saucepan of water to a fluid/gooey state, and poured over the master. When it cools it forms a flexible tool which can be used over and over, like a rubber moulding. Once you're done, you can cut the vinyl up, remlt it into a new tool.
It's rather like the wax method, but becuase it's flexible, the original can have sharp undercuts, and you can just peel it away. It's available in different grades, from super soft to something quite firm.
Can't recommend a US supplier. I got mine from Titanti in the UK. http://www.tiranti.co.uk/EdgeImpactShop ... cillaries+