Felt tip brush pens come in a array of colours, textures and sizes. My favourites are Royal Talens Ecoline Watercolour Pens for their bright hues and blending ability. The saturated pigment and wet nib glides effortlessly across the paper. While still wet, add a second and third colour to create a gradient effect.

Artline, Tombow, Pentel and other brands make similar brush pens with smaller nibs and equally saturated pigments — I love them all. Try them on smooth Rhodia or bleedproof paper for the best results.