Hi Zigried,
Welcome to AutogeekOnline! :welcome:
When you talk about "spots of dirt" in the context of removing them using detailing clay, I think the way most would describe the spots of dirt is using the generic term of,
contaminants
Could be lots of junk, like tree sap, paint overspray, industrial pollution, fallout, etc.
And - instead of trying to see them on any color you FEEL for them with your sense of touch as well as the baggie test. Like this,
The baggie test or even your hand feeling the paint will work like looking with your eyes.
And to be honest, I don't think you can clay a car and then do the baggie test and get to the point where you feel absolutely zero bumps on the paint, seems like there's always something somewhere that you can't get off. This could include tiny bumps in the paint from when the car was painted.
So don't drive yourself crazy aiming for perfection.
