I used a similar method as iscariot when I cleaned my pipe very recently, only instead of waiting overnight I shook the bag/pipe vigorously for a few minutes and then finished it up with a pipe cleaner and warm water. It took less than 15 minutes using this method to get my pipe back to pristine condition.

However, taking into consideration the multiple bends in the pipe, it could be difficult to get the alcohol-salt mixture to move through the pipe. For your piece, I might just try letting it soak. But there's no reason not to try knocking that res loose first. The solution will become pitch black after just a minute or two, but don't worry about it becoming less effective or leaving residue on your pipe.

As for Formula 420, I have never used it, nor do I claim to know anything about its effectiveness, but what I've heard suggests that it is likely a simple alcohol based solution with food coloring in it. Given that, I'm sure it works perfectly, but it's probably not necessary to go to the head shop and pick this stuff up when you've got the makings of it sitting in your medicine cabinet.