Apply acrylic wall glaze. Use a paintbrush to paint the mirrors and/or glass panes with the acrylic glaze. The glaze applies clear, so you must use clean, deliberate strokes to avoid unwanted patterns in the frost when the glaze dries and turns opaque. Allow a few hours for the glaze to dry.
Spray the mirrors and/or glass panes with frosting spray. The spray applies as simply as spray paint and results in a frosted effect on the glass. Be sure to do this in a well-ventilated area, and allow a few hours for the spray to completely dry.
Apply frosting film to the mirrors and/or glass doors. The film applies like a sticker, much like applying tint to a car windshield, and obscures the view. The film may be the most economical option, but be careful to avoid trapped air bubbles when applying the film.