No teaching of cosmetology, whether to students or licensees, is lawful except in a duly operated school; however, for purposes of this section, “teaching of cosmetology” does not include demonstrations of the technical applications of cosmetology products conducted by manufacturers or dealers, or both; provided, that only students or licensees are in attendance. “Teaching of cosmetology” also does not include instruction in new developments in cosmetology; provided, that the instruction is conducted within cosmetology shops and only students or licensees are in attendance.