OlFart describes the minimal method that is about the best you can do without removing the glass. I know from experience with our previous coach, a 2002 Journey, that if you can see rust when you pull out the rubber molding, there is a lot more behind the glass that you cannot see. However, it may be years before you develop a leak or the glass breaks.
'07 Country Coach Allure 470 Siskiyou Summit #31578, Cummins ISL 425; 2014 Ford F150 toad; Air Force One Toad Brake.
Glen Allen, VA; Smith Mountain Lake, VA.