Soak up as much milk as possible with a clean rag. Continue blotting until the rag comes back dry.
Moisten a clean rag with dry cleaning solvent. Sponge the dry cleaning solvent onto the milk spot.
Blot the area with a clean rag to absorb the solvent. Keep sponging on the dry cleaning solvent, then blotting with a dry rag until the milk stain is gone.
Combine 1 tsp. of dish soap (free of bleach and alkalies) with 1 cup of lukewarm water into a bowl if the milk stain is still there. In another bowl, combine 1 tbsp. of ammonia with 1/2 cup cool water.
Sponge the soap solution onto the milk stain with a clean rag. Blot with another rag to absorb the liquid.
Sponge the ammonia and water mixture onto the stain. Blot with a dry rag.
Repeat the process of sponging on the soap, blotting, sponging on the ammonia solution and blotting until the milk stain is gone. Rinse the couch by sponging with a clean rag and cold water, then blot it well to dry.