ako kasi, more on the preventive side. i don't smoke inside, nor open my windows kaya di naman masyado dumudumi yung ceiling ng car.
if ever magkaroon ng dumi, nililinis ko na agad yung affected area. i just use mild soap (Ivory) or shampoo, toothbrush with soft bristles and paper towels. just soak the brush with little water and soap then brush the affected area. wag masyado madiin and also don't let it soak in water for too long. use paper towels to absorb moisture.
kung medyo madumi na talaga yung ceiling mo, i suggest you let the professionals do it. mura lang naman pa linis ng headliner. i think it is around 1K..