Thanks. I do not have an airbrush, it is brush painted.
About the faux bronze for the base coat I used a mix of burnt umber, black and gun metal. Once set I applied a wash of (mixed) dark orange, old gold, gun metal and black. Some drybrushing with old gold, gold and bright brass, more washes and more drybrushing.
The marble has been painted using very thinned paint (through several layers) for the spots. Veins have been painted over the dried spots as well on wet over the glossy coat. Repeating the above steps three or four times ensures a good transparency effect, due to the layers of satin/gloss paint.