I came up with a slick trick years ago for Post '68 ('69 and newer) Windshield sealing... Use a bead of the 3M Window Sealer (The Butyl Dum Dum stuff), and then just outside of that use a nice bead of real Urethane. It will never leak, and the Butyl Dum Dum stuff is there like original plus it keeps the Urethane at bay from oozing in. Works great! Try it on your next '69 or newer windshield!...Plus when installed, You never even see the Urethane with the trim pieces installed.. Instead of using one or the other, Use both! It works great! ...While looking all original too!
PS: I've found plain old Gas or Ronson Lighter Fluid works great at a solvent... But once the Urethane is rock hard dry... Not much will take it off.. so be fast..