A.Jon Tobey, a painting contractor in Monroe, Wash., responds: Most of the time, a pressure washing with detergent solution is adequate for removing chalking and dirt from aluminum siding. Kill any mildew that's present with a 3-to-1 water-bleach mixture before washing.

If there is some water-activated staining that won't wash off, lightly fog the siding (at the rate of about 3 gallons per house) with a quick-drying alkyd primer. If you're brushing, you can buy aerosol cans of the primer and spray the stains with a very light coat (one you can still see the stains through). In rare cases, there may be some bare aluminum; if so, I'd try to find out why the paint is peeling. But in general, aluminum doesn't require any primer, as latex adheres tenaciously to the metal.

Then the siding can be painted with a high-quality 100 percent acrylic paint by brush or roller, or by spraying. I've had good success with Sherwin-Williams' SuperPaint; aluminum siding that I painted 10 years ago with this product still looks good.