the problems of watercolor painting proses because the watercolor paints is not of high hiding power, and past efforts can not simply be painted over, and the absorbent paper and is difficult, unlike an oil painting on canvas. Watercolor has a longstanding association with drawing, and sometimes we can make mistakes to make precise, make outline with pencil drawing of the object to paint, use small brushes and paint areas after dried.
Watercolor painting is traditionally, and always applied with brushes, buy you can make experiment and have combined with watercolor pencil, charcoal , pencils, chalk, ink, etching, monotype, lithography and collage, or with acrylic paint.