Scuff the surface of the satin paint with 80-grit sandpaper attached to an orbital sander. Do not place heavy pressure on the sander, as this may remove the paint rather than scuffing it. Work in circular motions, wiping the surface with a damp cotton rag between sanding to expose the surface and remove excess debris.
Wipe over the satin paint with paint thinner. Apply paint thinner to a cotton rag, and wipe down the surface of the old paint. This will soften the paint molecules and help the new and old paints bond. Apply only a small amount of thinner. Applying too much will damage the paint, requiring complete removal of the satin paint.
Apply two coats of oil-based primer over the satin paint. Use primer specified for painting over other paints rather than new surfaces. This type of primer has special bonding agents that will aid in connecting old and new paints. Spray on the primer, if possible, with an electric sprayer. However, if you must brush, apply even, smooth strokes to avoid paint marks. When painting over wood, lightly sand between primer coats with 120-grit sandpaper to remove brush marks.
Apply three coats of oil-based paint over the primed surface. Spray on the paint if possible. Spraying will eliminate surface imperfections and speed up the process. Spray in even strokes, holding the nozzle 8 to 12 inches from the painted surface. Otherwise, roll on the paint with a 12-inch roller. Alternate painting directions so as to achieve maximum coverage of the old satin paint. Allow one hour drying time between coats. Rub the surface of the dried paint between coats with #000 steel wool to smooth the surface and to maintain a bond between each coat.