Thanks for all the replies!
First of all, I’m already thinking of a followup article, with some more advanced things, like dirtmaps, and modelling cracks, but that will have to wait for a few weeks (exams and stuff…).
The Kiwi: well, that’s why I like Yafray’s GI. If you set the emit parameter of an object other than 0, it will actually emit light, although you can barely notice it. You do have to set the GI strength and the Emit strength in the Yafray GI settings panel very high for a nice effect.
You can also fake this with the Glow filter in the sequence editor if you don’t want to use Yafray, not as nice though…