When it comes to marking on rough surfaces, graffiti artists need markers that can produce bold, visible lines. Paint markers, with their paint-like consistency, tend to be a good choice for marking on rough surfaces as they can create bold, opaque lines that stand out. Spray paint cans can also work well on rough surfaces, providing a more vibrant and wider color range than markers. Marker pens with waterproof and fade-resistant ink may also be a suitable choice, though they may not provide the same level of boldness as paint markers or spray paint. Ultimately, the best marker for rough surfaces will depend on the desired outcome and the artist's personal preference.