I love using Kuretake Zig Memory System Brushables Dual Tip Brush Pens for both calligraphy and coloring. One thing I like most is that each pen has two tones. One side features a darker color shade and the other side a lighter color shade which makes it suitable for writing shadow letters as well as creating two-toned blending effects. These pens have a soft brush and medium size brush tip which allows you to write bigger size of lettering.
I also like using these dual tip brush pens for water coloring. With the use of a Kuretake water brush pen, watercolor effects can be created easily. There are different ways of doing it. After coloring your picture with the dual tip brush pens, fill the water pen with water. Wet the tip by squeezing the barrel. Then apply on your coloring. Another way I like is to draw some colors on a plastic sheet in advance, then color your drawing with a filled water pen. Both ways create great watercolor effects.