what seam sealer?

Another vote for brush-able seam sealer. Sets in a reasonable time and is very tough. It's just like the factory stuff. 3M Fast-n-Firm in a caulk tube is horrible. I've also used a urethane seam sealer in a aerosol can that comes out like Cheez-Whiz. Course, it's more rubbery when set. And the two part seam sealers are outstanding - cure very quickly, but are pricier and require a special (read:expensive) gun to dispense.