In Chinese medicine, facial exercises are recommended. Specifically recommended facial exercises include acupressure on the face, massage of the face, and specific facial muscle exercises.
Facial acupuncture may or may not help.
Specific facial muscle exercises for drooping lower lip are (1) acupressure of the two points at the corner of the mouth, and (2) smiling or forcing a smile. Smiling pulls the lower lip up. And (3) Facial massage, because it can stimulate facial muscle movement, and bring in more circulation of blood and oxygen to the facial muscles.