Pressure wash the house to remove dirt, mold and mildew and provide a clean surface for the paint to adhere to.
Scan the siding for any loose or flaking paint and keep an eye out for bubbles in the paint. Also note any holes or gouges in the siding.
Remove loose, flaking or bubbled paint with a paint scraper. Hold the handle firmly and pull the blade across the defective paint. Keep the blade as close to a 90-degree angle to the siding surface as possible.
Fill any gouges or holes with an exterior wood filler. Allow to dry and sand smooth with 120-grit sandpaper. Skim coat the areas where paint was removed.
Caulk all joints where the siding meets other pieces of siding or door and window trim. Do not caulk the joints where one piece of siding overlaps the siding below it. This will trap any moisture that may get behind the siding and potentially cause rot or mold.
Examine the bottom edge of each piece of siding. If the edges are starting to show any sign of delamination--cracks running lengthwise along the siding--caulk the bottom edge to fill the cracks and help prevent moisture from entering and further delaminating the siding.
Spot prime any caulked or puttied areas, as well as any that are missing paint, with exterior primer and a paint brush. Since the pressed wood siding is already painted, only the bare areas need to be primed.
Paint the siding with a brush and exterior acrylic paint. A wider brush will make the task go faster. Or use a brush to paint the bottom edge of the siding and around any joints and then a roller to paint the face of the siding.