Is blended filament good for rough surfaces?

Yes, this is one of its key strengths. The increased stiffness and abrasion resistance of a blended filament (like PET/PBT) allow the brush to work paint into uneven surfaces, such as stucco, weathered wood, or concrete, without the bristles bending excessively or wearing down quickly. It is an excellent choice for exterior painting and other heavy-duty tasks.