This is drop dead easy. After making a two litre batch of yoghurt, I hung one litre using a piece of cheese cloth and a tea towel and left for around 3-4 hours. The yoghurt thinkened up beautifully and has that wonderful sharp flavour that greek yoghurt has.
Will definately do this again as Greek yoghurt is my favourite.
The photo shows the yoghurt before and after hanging.