Originally Posted by Square Eye
Tsp or Superclean and a sponge. Sometimes a Scotch-brite pad. A light stream of water is all you need for soaking and rinsing.
Then latex exterior paint. Latex doesn't get so hard and peel off like oil does on thin metal.
Square Eye is right on! I would certainly use TSP, because it will remove any chalky paint. It will also remove mold/mildew is mixed with bleach, but make sure the brand you use can be mixed with bleach (most can).
When spraying latex make sure you get a sprayer that supports a 621 tip size, especially if you spray latex primer first! Priming isn't a must, but primers have more binders in them than pigment, so the odds of peeling with be greatly reduced!
BTW, Square Eye for the Tool Guy! Funny!!!