I found butyl a bit too difficult to
work with over large surface areas such as
deck organizers. I've recently had reason to pull all the
deck fittings, many of which I'd rebedded a few years back with 3M 4000. I really, really like this stuff. You squeeze it out, tighten the through bolts tightly (one time) and make a nice clean-up line from the squeeze out. It makes a great waterproof seal. It was a bit hard to get it to release, but it didn't cause any damage. Heat works, too.