I like Minn's idea, The nailpolish idea has 2 things working against it. One, the covering by nature will not accept paints. Ultracote will after some scuffing but hadhision is not ideal. Two Nailpolish is not fuel proof. IMO you would be better off keeping a coat of wax on the airplane thus providing a barrier so fuel can't get to the seam. I actually have never had an issue with seams coming up provided they were put down correctly in the first place. Keeping things clean during the covering process helps this greatly.