Well, I'm not kidding. Any professional/ serious self-taught artist knows what 'fat over lean rule' is. I challenge you to ask a new painter to know what the art technical term is. If not, you're at your own risk. I bet your father's best friend obviously has no idea what it is. Numbers of clients ask me to fix their paintings because they got rip off by untrained painters. I tell them I can't save their paintings because I have no idea what mediums, gums, resins and primers untrained painters used on. Did they use alkyd? Liquin? linseed? Turpentine? What brand acrylic? Rembrandt? Varnish? Gesso? Rabbit-skin glue? They give me those blank looks and have no idea... :/
When a client asks me for commission, but I have to be frank and ask directly-Where do you hang your painting? How do you take care of your painting? I educate them and give them instructions, so they can take care of it properly for lifetime. My job is to make sure they protect their investments for their sake. Clients LIKE to touch on originals. They just can't help it. It is in part of my contract my clients require to sign that I won't be liability for their careless acts.
Some clients told me do hang their original paintings in the bathrooms. Wrong on many levels. Humidity can damage originals. I always suggest that they can use art print instead for bathrooms. Don't let sunlight hit original oil painting directly ever. The colors will change over the time I'd say about in several years if it continues to be exposed to the sunlight. That's why museums and galleries use very low light and have windows shut.
That's just FYI....