Denatured alcohol is very nice and will evaporate quickly.
It's kinda like rubbing alcohol but stronger and will work much better.
A air compressor to blow the dirt off also helps, but if your don't have access to one, and spray bottle and DA(Denatured Alcohol) will work great.
My exhaust pipe on my Revo was almost black with junk. I tried engine degreaser, carb cleaner, and even brake cleaner tried to scrub it off with a wire brush with all of them. Then I bought some denatured alcohol and simple green made a 50-50 mix and spayed it on and just wiped it with a paint brush and it came right off. I have since made that my official cleaner