Water-based paint demands high substrate cleanliness; dust, oil or residual release agent lowers adhesion and causes craters or bubbles, so clean thoroughly and sand or degrease if needed. Ventilation: although VOC is low, small amounts of harmful gases (ammonia, alcohols) are still released; good ventilation speeds water evaporation and reduces buildup, but avoid direct strong wind that dries the surface too fast and hurts leveling. Equipment: water-based paint corrodes metal equipment (spray guns, pipes), so use stainless steel or anti-corrosion materials and clean spray equipment regularly to avoid clogging nozzles.