industrial design hand-drawn with what pen, with watercolor can be

Can, hand-drawn words with a neutral pen, ballpoint pen (red and blue), syringe pen, pencil, carbon rod, colored pencil, watercolor are line, as long as the drawing out of the things can be expressed clearly on it, because we can not be and have learned the art of the same drawing is very realistic, to the aftermath of the general just sketches are the most important, the effect of the drawing generally have to be modeling and rendering

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