This handwash paste is a well-tried traditional hand cleaning stuff for oily, greasy hands of a restorer or the hands of a hard working gardener. I even heard some one tried this for 'peeling' - but I do not recommend this.
It is normal that the paste gets hard by time. Then just add a few drops of soft soap or water and steer until it gets soft again.
I know there will be cheaper 'Washsand' on the market, but what are You doing with a 10kg bucket at home ?