Soot spots on trailer roof

[woodie]

I live near a Plywood Mill and we get pollution from their smoke stack in the form of a black dust that settles on everything.Also soot spots on our cars and the trailer roof.It all will wash off, but the soot spots takes a lot of scrubbing before it comes off.With my bad shoulder I have a heck of a time scrubbing and cleaning the roof of the trailer.Any suggestions for something to make the soot dissolve or soften to make it easier to wash off, that won't damage the fibreglass?