It was really easy to use, and worked really well - don't expect to be able to mould yourself an entire army, however, as the effort and green stuff required really wouldn't be worth it!
He'll get a better paintjob when I decide on a paint scheme!
Note that I managed to get ink from the instructions on the gel, but it came off with some more hot water. This stuff is a lot better than I thought it would be. I don't think I'll need more than this one bar of it however, as it's reusable. Score.