I attended a short workshop to learn porcelain decoration/painting with Erika Albrecht at Arch 40 (East London). The surface was VERY smooth and the control of the brush was actually very difficult. However, erasing was very simple, just wipe it off with some tissue!
After 2 hours of practising on the flat plate, we were given a cup to decorate and eventually to take it home! This is what I did in the end.