To paint over ANY surface, without sanding, use a product called 'ESP Easy Surface Prep', available at hardware and paint shops. Wipe on, wipe off and paint in 90 minutes. Works well over enamel paint , without having to sand. SAVES HOURS of work. It was recommended to me by a professional painter.
Soak steel wool in apple cider vinegar, rub down new wood with the Soak steel wool for an instantly aged wood look. Good to know for "vintage" signs.
Easy tutorial on repainting & distressing old furniture