Making plastic glossy is done by using a process called buffing to remove a dull finish and scratches that appear on a surface. Buffing involves using a polishing compound and elbow grease to restore a glossy finish. Materials you need can be found at your local hardware, automotive or home improvement store.
Clean the surface of the plastic to remove any grime and dirt using dish detergent and warm water.
Apply a small amount of polishing compound to the plastic, according to the label directions. Rub the compound onto the surface of the plastic a circular motion. Wait 3 to 5 minutes for the polishing compound to set.
Rub the compound from the surface with a clean cloth. Rub the surface using the same circular motion to restore the gloss to the plastic.
Repeat this process to restore the gloss to another piece of plastic.
Be sure to use polishing compound, not rubbing compound. Polishing compound is less abrasive than rubbing compound.