Making a new Lee pot of isocore today and dumped in ~4# of dross from previous sessions. You know, the crumbly junk that won't go back in. C.S. on top of it, remove the powder and WOW, clean alloy, no dross, just powder! Don't ask me what it does, I'm no chemist but it did work. I used NO sawdust or other 'flux'. I did use some beeswax after it get 'cleaned'.
edit: I use CuSo4 (C.S.)to add Cu to my alloys. Just dump on top and stir in (carefully, H2O is a byproduct).