I too have older white aluminum siding, and the paint is so thin in some places that the aluminum shows through the paint. The majority of the siding (entire house) is chalking. Otherwise, the siding is in good condition (a joke!). I would like to paint it or have it painted, but find few people who desire to tackle it. I've been told that it should be washed down with some type of preparation prior to painting, but don't know what it is. Have you received any answers since posting your dilemma? Anybody out there have a response?