I think I found this link on this very forum.  I have yet to look into it.

http://www.streakmaster.com/index.htm

I use Blacksteak remover straight up and rinse it off quickly.  I have used soft scrub on stubborn areas.  I like the mild bleach affects on green moldy areas.

I have one of those soft RV extendable brushes.

My fav weapon is my power washer on the extruded aluminum areas and under carriage.

Lots of elbow grease but if I keep up on it it actually stays pretty good.