i usually just skip on the salt tbh, i just use some extra solvents instead and some heavy shaking gets the job done pretty well instead of having to use the salt.. i used to use the salt, but i didn't really see much of a difference with it, so i figured i'd save the salt for the corn on the cob instead of my glass..
i've also found it you let the glass soak for a good 10 / 20 minutes or so first, it also helps to loosen up any stubborn pieces.. not sure if you're cleaning a bowl or a bong or what, but usually when i clean a glass bowl, i'll just fill up a bowl that the bowl will fit in, and place the bowl in the bowl and let it soak for a while first.. than i do the heavy shaking, usually trying to keep the solvent in the bowl the entire time i'm shaking too..