If it's still soft then it's easy, just pull the glass out and use good paint scraper (?) with rounded corners to avoid scratches and sand slightly before doing it properly again. Using too much hardener on the other hand may take lot more effort and it's not even easy to spot, so if mix ratio is not perfect it's better take it too soft <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />.