There are several quality seam sealers. One not mentioned yet is Silkaflex 220+. It is used primarily to glue in windshields and sticks to almost everything. While wet, it cleans up easily with mineral spirits. I have used it successfully on all my skoolie windows as well as a seam sealer. The material can be painted with anything once cured and after 5 or 6 years on my bus it still looks and performs like new.
Regardless which sealer you choose, through pre cleaning and sanding to remove dirt, old sealer and dead paint is a must.
I've found it cheaper to buy from a local windshield guy than from ebay or amazon. Jack