When you notice the paint getting stiff or dry give it a quick mist. You will find you will save paint and always have moist color to work with. To keep paints moist for an extended time period, spritz with water, cover with plastic wrap and place your palette in the refrigerator. The paint will stay workable for a number of hours in the cool, damp environment. By placing a wet sponge in with the paint, the colors will stay moist over-night.
All polymer clays are compatible.
If you want your airbrush to work well and provide you with years and years of faithful service, keep it clean. First spray any paint out of your airbrush. Spray plain water through it until it sprays totally clear. Soak for 30 minutes. Spray with water and your airbrush will be back in business.