Allow the melted Styrofoam to harden on the surface of your couch. Apply a plastic bag filled with ice cubes to speed up the process.
Remove the bag of ice from the hardened Styrofoam. Sand the hardened substance to wear it down as close as possible to the couch upholstery.
Vacuum the surface of your couch with a hand vacuum to remove the sanded Styrofoam dust.
Pour 1/8 cup of acetone-based nail polish remover into a shallow bowl. Dip a soft scrub brush into the nail polish remover to dampen the bristles.
Scrub lightly over the Styrofoam residue to dissolve the remainder with the nail polish remover. Wipe the couch with a dry cloth.
Pour 2 cups of warm water into a bowl and add 1 teaspoon of dishwashing detergent. Dampen a clean cloth with the detergent solution. Sponge the couch upholstery to wash off the nail polish remover.
Rinse your couch's upholstery by dabbing it with a damp cloth. Press a dry cloth into the surface to absorb moisture. Let your couch air dry completely.