“We do not see the world as it is, but as we are.” — Anians Nin And you do not know what you feel before you felt.
Using Persuasion Techniques to improve the Sex Appeal level of your Romance novel characters, is not only fairly simple, it's effective and invisible to the flow of your writing and the rest of the storyline. The focus, is the reader. Your characters can look and read sexy with their moans and sighs, but it’s only sexy if the reader screams for real.
To write is to persuade. To persuade is to make a connection and if you want to motivate then that connection will have to be an emotional connection. If the goal of your persuasion is to keep the reader turning pages, the path is the same.