Oh there actually are recepies for this kind of stuff.
Afaik it's essentially very fine iron dust in some sort of oil or variations of that.
Just google around a bit and you'll sure find some recepies.
It was quite a while ago now, so maybe there are some recipes about now. We found a few sites and got some fine iron dust, but the dust needs to be nanoscale and all completely coated in a surfactant to stop them clumping together and then suspended in a carrier fluid. We had tried a few different things, but none of them worked in the same way as the quantity I had bought. It was the lack of the surfactant that seemed to be the problem, and finding out what is used and how the particles should be coated was fruitless and so seemed pretty futile for a home brew project, so we gave up. Mind you as I said that was some time ago now so I might have to go trawl the tinterweb and hunt down this illusive surfactant.