Hi Fred: That's a good question. By "detailing finish" you mean they've already applied some sort of beading agent to the windshield? If so, how does it work? Or do you mean something like this stuff from Eastwood: http://www.eastwood.com/shopping/product/d...iProductID=2012 If it doesn't work that well, try just a very small corner of the windshield first with Rain-X. If it seems to work, then carefully clean the entire windshield and treat it. Hope this helps. Jay
