There are paints you can use to waterproof wooden furniture, but if you would like to waterproof upholstery, you will need a completely different product. There are sprays on the market that use polyurethane as a base to ensure that water runs straight off the natural and synthetic materials from which your couch cushions or favorite lawn chair pillow are made. These are readily available at most home improvement stores and are often overlooked, but they are extremely useful to have on hand.