When flatting a new paint job, how do I know if I'm sanding through the clear coat?

I spraypainted my fibreglass bumper with an acrylic clear coat and I'm about to flat it with 1500 wet sandpaper. When sanding it, how do I know when I'm sanding through the clear coat? Does the clear coat come off with 1500 sandpaper?





How hard should I be rubbing it?When flatting a new paint job, how do I know if I'm sanding through the clear coat?
if the cars not white and the dust coming off when sanding is white, then its just clear coat. when you start to see the cars color in the dust then you know that you went through the clear coat. clear coat is sort of thick, so just go till its flat. dont push really hard but at the same time dont just rest the sand paper on it and move it, sand it with a bit of pressure.When flatting a new paint job, how do I know if I'm sanding through the clear coat?
YOU MIGHT HAVE TO WET SAND IT.I REALLY CANNOT SAY,BUT IF YOU LIGHTLY RUB UNTIL IT IS SMOOTH THAT SHOULD BE ALL YOU NEED