I wonder if she is talking about this technique.

Cissing - is a mottled paint finish created by overlaying coloured glazes and partially lifting the colour with a solvent.

Cissing is done by scattering mineral spirits on oils, and water on latex. To give a natural stone or limestone-like effect, colours suggested are pink, beige, grey, oyster or ivory, charcoal and grey-green. Colours will seem to fade as they dry, but can be brightened with a coat of polyurethane.