Fish-eyes, craters, webs, veins-all ugly. They make deluants and additives to help eleiminate the problem. Celusolve, Silflow, and anti-crater are all good to use in the topcoats. Also, I suggest not sanding the undercoat too smooth, as when it is very slick, the new coat can literally not wet the surface(reticulation) and causes a spider web effect sometimes. A 220 finish is about right for recoating. Painting is a very ornery sport. Also-try a linear urethane coating sprayed-up for the top coat(if safety equipped).