I agree with Russ, however if you do come across soot on aluminum or vinyl, I have had good luck with Hydrocloric Acid. I like to use the buffered stuff, it is a lot more expensive but safer and more stable than the stuff you can get at you local hardware store. As always do a test spot. At 2 years old you should be fine but aluminum can get chalky quick and you might end up having to acid wash the entire side of the building to blend in one small spot... Just my 2 cents.