You can paint with both instant and regular coffee. You can save a lot of time by just dissolving some instant coffee in hot water. To get a lighter or deeper hue, alter the coffee/water ratio. Less water will be needed for darker colors. You can always add water to your paintings, just like with watercolors to create lighter values.
Granular filter coffee requires more time to dry than regular coffee. On the other hand, instant coffee is powdered, sticky, and more manageable.
