Decorating & Furniture/Painting over different furniture finishes
I have three pieces of furniture that I want to paint. One has already been painted and sealed, one has a polyurathane finish and one is manufacture-finished. How do I prepare these different surfaces for painting?
To repaint furniture that has already been painted and sealed with acrylic varnish, simply wash the surface with a damp cloth wrung out in hot water and dishwashing detergent. Do not soak -- the intention is simply to remove any dirt and grease. Leave to dry. Rub the surface down with medium-grade sandpaper and clean off the dust. Paint with acrylic primer in preparation for painting later.
To repaint the piece that has been painted and sealed with polyurethane varnish, wash clean as described above and, when dry, sand with medium-grade sandpaper to provide a key for painting. Then sand a bit more. Clean off any dust. Paint with aluminum primer to prevent any discoloration coming through subsequent coats of paint.
For the piece that is manufacture-finished (I am assuming laminated?) I would sand it quite a bit then I would apply Kilz Primer (water-based is fine). Then wait for that to dry. When the piece is dry I would apply a better quality paint-several coats- sanding after each coat. Still, though, you may find that it is susceptable to nicks. So I would advise you to save the paint you buy in a sealed container and sand and repair this piece when and if it needs it.
I hope this was helpful and good luck with your painting and decorating,