Last week Olga, Irma and myself took a look at the sorting process. Once the sheep are in the huge circular pen, they are sorted into wedged shape pens that are around the edge...Olga has a great diagram on her blog from a couple of years ago here. Each farmer has their own wedge pen and they identify their sheep by tags, ear markings or like Olga's uncle just by their faces...they are then dragged, pushed, shoved into their respective pens...gently of course.
Usually you just look for your own sheep but some of the kids tend to just grab any sheep and then struggle around with it looking for the right pen...it's no fun unless you are hanging onto a sheep.
Here is a little video I took when we were in the circular pen with the sheep