at least the tech with SW paints, claim that anything you add to paint will cause something to be altered and change molecular structure.
The exceptions are: with oil, Japan dryer is OK, with latex, emulsabond and others are OK.
They even deter you from adding water to thicker paint to make it more acceptable to HVLP spray rigs. They make paint for hand and for rigs. IE, Super Paint is too thick for rigs and good for by hand, but A-100 is just right for rigs.
To get to your subject, be careful what you add and the result you migh achieve. I as a paint contractor would not be held responsible for the surface paint job if I was told to add talcum powder to the paint.