Yea it's really easy to make. It can either be done with liquid glucose (you can buy in bulk from cake-stuff.com I think) or corn syrup (amazon link above). I've only ever used corn syrup. You just melt the chocolate, let it cool for as long as possible (but don't let it solidify) then stir in the corn syrup. Pour it out, get it into one big ball and wrap it in cling film and chill it. Cocoa butter oil will leak out of it, losing some isn't an issue.
When I made mine it set rock solid at room temperature and when warming it enough to kneed it just got oily again (maybe I overheated it...) the only way i could get this to work well was to mix it 50-50 with sugarpaste, it was great for covering and for roses (see http://cakecentral.com/gallery/2400199/well-i-made-my-own-wedding-cake) but I'm finding with playing with the leftovers that its too soft for making figures and I can't get a really smooth finish... did I make it wrongly do you think or am I comparing it too much to SFP?
The corn syrup was a great suggestion, way cheaper than glucose and worked great thanks Kim!