Protect the surrounding area around the sofa. Lay down a plastic drop cloth to collect any spills of excess paint. Use painter’s tape to cover any areas of the sofa that you do not want to paint, such as the arms, feet or piping. Paint only in a well ventilated space or outdoors.
Spray the surface of the sofa with fabric paint. Keep the nozzle of the fabric paint about 6 inches away from the fabric of the sofa to apply the paint as even as possible. Move steadily along the surface of the fabric.
Allow the paint to dry fully. Mop up excess paint with a sponge and remove the painter’s tape. Be aware that even if the sofa fabric is dry, some moisture might have penetrated to the underlying foam and batting, so be sure the sofa is completely dry before you use it.
Weigh the slipcover. To determine how much dye you need for this project, use the ratio of 1 ounce of fabric dye for every pound of material. If your color does not fully cover, more dye will be needed to reach to saturate the slipcover to the color you want.
Fill a large tub with warm, 75 to 80 F water and fully submerge your slipcover. Allow it to soak for about one hour, then remove it and wring out extra water. Add more warm water to the tub.
Pour cool-water liquid fabric dye into the water. Use a large spoon or mixing stick to disperse the dye through the water.
Place the slipcover inside the tub. Avoid crumpling up the fabric so the dye can penetrate evenly. Use the spoon or mixing stick to submerge the slipcover, stirring it frequently. Allow it to set for several hours.
Repeat until your sofa fabric is your desired color. Once the fabric is saturated to your satisfaction, thoroughly rinse the slipcover until it runs clear in cool water.
Set your dryer to optimum dry and place the slipcover inside. Let it tumble dry and de-wrinkle as much as possible, though it is likely some wrinkles will remain. If your dryer is too small for the slipcover, either hang it or lay it flat to dry. Press with an iron when it's dry to further remove any wrinkles.
Arrange your slipcover over the sofa. Once your slipcover is in place on the sofa, use a steamer wand to press out any remaining wrinkles.