The cracking is "Ball swirl" - and usually, removing the dirt in other colors is easy, as the dirt is black. The Magic Eraser removes the black dirt from the clearcoat or varnish. The color behind it "highlights" the dirt in the minuscule cracks. When the "ball swirl" is evident on black art, then there is the problem as highlighted in picture 13. The "ball swirl" cracks are present, but there is no dirt in them - just the cracks themselves. There is no way other than sanding off the clearcoat, to remove the cracks - this is true for all "ball swirl" - you are NOT removing the cracks, just the dirt deposited in them.

Black just highlights the cracks.

By applying paste wax and buffing, the cracks are less predominant - the wax is "soaked" into the cracks - but it does not completely fix the issue.

I hope that makes sense.