making a mould for green stuff

i seem to have lost the post i did for this so apologies if i am double posting.

Thinking about a Sisters warband, and i would need a lot of identical Sigmarite Warhammers.

So how would you go about making a mould for green stuff hammer heads that the gs wont just stick to???

TIA

instamold/bluestuff. easy, reusable, and a great start for low prices.
http://shop.greenstuffworld.com/making-mold-material/blue-stuff-mold-8-bars


it is a tiny bit tricky to start off as it sets very quickly, but as it it reusable, it only takes a couple of hours to get the hang of it. such small items are a great start to learn how to work with it.

I am in no means an expert on casting, but I've used this stuff for some time now, and it makes for easy copying.

Thanks Ezekiel, i will try some out.

instant mold is the best. and when you start to get crazy switch on over to milliput from gs to keep cost down