You may apply corn oil to the hair and leave overnight. Or you may use corn oil as a hair conditioner. It is a good idea to warm up the oil as it will penetrate the hair better.The oil amount depends on your hair length, but don’t add too much.ot oil conditioning. You may apply corn oil to the hair and leave overnight. Or you may use corn oil as a hair conditioner. It is a good idea to warm up the oil as it will penetrate the hair better. The oil amount depends on your hair length, but don’t add too much.