i always use oxiclean, and it gets my glass pipes spotless ( i have four). i boil some water on the stove, get a bowl, put a couple of tablespoons of the oxiclean powder in it, pour the hot water in, and then i always wait a few mins, add a little bit more oxiclean, and put my pipes in the water. and then i usually am baked and i forget that they're in there...so i always let them soak for different times lol. but yeah, if they're not completely clean when i take them out, i run hot water through them and then they're spotless!

here are my pipes, after cleaning them with the oxiclean: