our home depot sells plaster sand that is called just that "plaster sand" it comes in plastic 50lb bags it is a bit too yellow for me but makes rockhard plaster, so i go to stone suplier he has whiter one.I am building vbulletin based fresco dedicated forum it has subscribtions and public areas I am going to ask you if you want to participate when the structure is ready.
and yes we shall talk about marketing things...