Pencil brush - Shake container well.Using the brush in the cap apply directly onto the rusty area, working well into any pitted areas, corners and edges. 100/250ml - Shake container well and pour required amount into a plastic container. By brush: apply direct to rusty area, working well into heavily pitted areas, corners and edges. Avoid coating onto painted areas. Hammerite Kurust will turn blue/black when reacting with rust. If it does not change colour in 1 hour re-apply. Apply topcoat after 3 hours. Do not replace unused Kurust back into the original container.