I think LTP meant add white paint to the dheneb stone.So basically use dheneb stone, then use thinned skull white, applying around 5-6 layers? how thinned should the paint be ideally? or is that entirely up to me?
So paint 1 layer dheneb stone, 1 layer 80:20 dheneb/white, 1 layer 70:30 and then keep going until the white is as bright as you'd like it to be.
I may well be wrong, but that method makes sense to me.