Acrylic paint is a fast drying paint containing pigment. It is safe to dilute it with water, but will become water resistant after drying. A common interior house paint may contain both acrylic and...
It depends on what the helmet is made of, and the use for the helmet. Acrylic paint will stick to most non-oily surfaces, but will easily scrape off of slick and non-porous things. If the helmet is a...