The Koi Blender is the best tool for mixing colours and to create fading swipes. Use the tip of the Colouring Brush Pens to put colours on a plastic palette. The ink will not dry so you can absorb the colours by using the Koi Blender. Use the Koi Blender as a brush by taking some colour from the palette and putting it on the paper. Start where you want the darkest colours and keep going until you get the desired effect.
Another effect is the combining of colours with the Koi Blender. Simply push the tip of one or more Colouring Brush Pens against the tip of the Koi Blender and it will absorb and blend the colours! To clean the tip, keep drawing on a piece of paper until all the ink is disappeared.