Spray down the piece of upholstery using a mold and mildew remover, and wipe it down with a clean rag. Pay attention to seams to make sure all of the mold or mildew is removed.
Spray down the surface using the vinyl prep soap to remove any contaminants that might be on the vinyl upholstery. Scuff the vinyl with a gray scuffing pad, making sure to get between seams and gaps in the upholstery. Remove all of the soap with a damp towel.
Spray the entire surface with the vinyl prep spray, then wipe away with a clean, damp towel. Mask off any areas that you don't want dyed using the masking tape.
Shake the can of vinyl dye, and hold it approximately 6 to 8 inches from the vinyl surface. Spray the dye onto the vinyl, applying a thin coat of dye to the finish. Allow the dye to dry for five to ten minutes, then apply a second thin coat. Repeat this process until the vinyl has an even look to it, and there is no splotchy coloration differences. Wait 24 hours before sitting on or using the vinyl upholstery.