As someone that has told several friends I am a nudist, I am not sure that all of this advice is good. For example:
Use the International Naturist Federation definition: « Naturism is a way of life in harmony with nature, expressed through social nudity, linked to self-respect, tolerance of differing views together with respect for the environment ». Naturism is shared by millions of people worldwide and there’s nothing wrong with it. It’s legal in most countries.
I suppose explaining that it is a thing in other countries is a good conversation starter. I usually don’t have to address the legality. Most people in my circle seem to know that being naked on private property or in most natural places is legal. Explaining the “official” ideology of INF won’t work on anyone.
Just tell people you like to go skinny dipping. You’ll be surprised who asks to come along.