On my first kayak, I took it to an automotive shop for varnishing.

I assumed they would sand the epoxy smooth, they had never done a kayak before, were nervous of damaging the glass, and only gave it a light sanding before working hard to achieve that perfect "inches deep" lustrous finish.......... adding seven kilos of two-part varnish! (dry weight, they actually used 14 kilos of varnish)

I am now sanding my third kayak, and have just sanded into the glass on a spot where the weave was not quite fully filled.....

Moral of the story is, make sure your fill coats are enough, add some epoxy where the weave is showing, after giving it a good scrub with a scotchbrite and water to get rid of any blush or dirt. And be careful when you sand before varnishing.