One method of applying paint to a sandcarving project is by airbrushing. The hand motions of airbrushing are similar to blasting, but require a bit more finesse.
Most airbrush paints are water-soluble these days. A good double action airbrush costs around $100 to $150, but you can use the compressed air from your blasting system to power it.
Learn more about applying paint to a sandcarved item.
—Professional Glass Consultant