I am planning a split mould too, and was thinking I will go one of two ways. Either envelope bag the whole thing like matthieu said, probably easiest and will result in least headaches....

Normally silicone is selfreleasing to most materials and epoxy is normally one of them... 

So, I have a large split mould that I'm bringing together to finally infuse. I've ran a bead of silicone between the mating flanges to help defend against air ingress. A tiny bit of silicone squeezed out onto the mould surface.