Although wax is usually not necessary to protect painted furniture pieces, it probably won't hurt them either. If you choose to wax your oil-painted furniture, do so no more than once or twice a year, and use a high-quality, silicone-free wax. Rub a thin layer of wax on the furniture with a clean, soft cloth, and allow it to harden slightly before buffing it to a shine. Applied this way, the wax wears off slowly, without the worry of a wax build-up. Use a white creamy wax on a light-colored table. Darker waxes can discolor the paint.
Avoid lemon oil or spray polish on painted furniture. Lemon oil can darken the furniture, while most polishes contain silicone, which creates shine but doesn't protect the wood. Silicone is also very difficult to remove if you ever decide to refinish the table.
Oil paint provides a protective coat for wood furniture, eliminating the need for wax. However, painted furniture does collect dust and grime. Wipe the furniture frequently with a damp cloth to remove dirt, and use a gentle household cleaner or soap if necessary. Wipe the furniture dry with a clean cloth. Avoid using abrasive pads and cleansers which may dull or mar the painted surface.
To prolong the life of your painted furniture, avoid placing it near heat vents or in direct sunlight. Use a humidifier if the air is very dry to prevent cracking and splitting. Use coasters and tablecloths to protect painted wood furniture from moisture condensation on glasses and vases. Re-touch worn, oil painted furniture yourself, or send it to a professional.