to begin with as far as I know in the US at least you are not washing "Paint". You are washing a thin layer of plastic which is applied over a base color coat of paint. It is the plastic coating over the paint base coat that gives it the shine.
Yes I would be careful what you wash it with. I only use a mild general purpose liquid cleaner like Amway LOC, (liquid organic cleaner) which I get online. I like this cause it is not a petroleum based cleaner. I would not use any Petroleum based cleaner on my cars.
It is so mild you can shower with it, wash your hair, clothes, pets and your baby. It has surfactant qualities that make water 500 times wetter.
For more info you can Skype message me at towjoe42930