Regarding an oil like substance falling from the sky during a cataclysmic event, our own site talks of fire in the sky and fire falling from the sky as do many other prophecies about end times. So my ideal clothing concept starts with an Arabic style garb with cape/head cover, made of say an aluminized material like the popular space blankets. This would all need to be water proof and possibly oil proof and able to insulate against heat and cold. Possibly some commercially available items such as ocean going long distance sailors use might be a starting point, also in Australia a popular outdoors stockman's coat and cape made of super tough, waterproof material might be considered.
Offered by Darryl.