Aluminum Siding:
If you have to paint on aluminum siding, you should give it a good cleaning prior you begin. Use a high-quality soap and scrub the surface where the aluminum siding is located. Rinse off the soap where some of the piant may come off. Let the siding dry for a few days (generally three to five) and apply a thinner to the surface. This is a very strong product, so be sure to cover your mouth to prevent inhaling fumes and be sure to take breaks (when neccessary).
Let this dry for 48 hours and then you can begin to paint your surface. Use an acrylic latex exterior house paint with a high-amount of resin, which allows for a longer lasting paint job.
Tips:
Do not remove aluminum siding or apply paint in direct sunlight or on windy days. These conditions make it difficult for paint to dry properly.
Days that are cool and overcase are ideal for painting aluminum siding.