Run your pipe under hot water in the sink, maybe set it on a towel so it doesnt' roll around and break while falling into the drain, thin glass doesn't take much to break it. Don't be a dumbass and boil it, you have to handle the pipe afterwards and it makes the house stink alot worse than just hot water under the sink. Besides, hot tap water will be enough to get it prepped.
Now put rubbing alcohol and salt inside leaving a void so it can slosh around in there, but not just any salt, KOSHER SALT, again this works better if the glass is warm from the hot water. Regular table salt doesn't have the same cutting power. Really, they are worlds apart in comparison when cleaning resin. Put your finger over the mouth piece and your thumb inside the bowl, and shake that bitch like it owes you money. Change the position of the pipe and the motion in which you shake it(swirl, switch hit, whatever you gotta do), you have to create the right kind of flow inside your pipe so the kosher salt can have a chance to rub up against all surfaces. When finished flush with pure rubbing alcohol and then follow with just hot water.
It should look like the day you bought it when you are done, assuming you bought it new.
Basically same thing as the salt and rubbing alcohol, but i really prefer the fruity smell while im cleaning my pipes haha. Hate the smell of rubbing alcohol >_<
