Glass cleaners work great as well. You could use Aqua Glass Works Cleaner or Wellcann Glass Cleaner. You can also buy cleaning solutions specifically made for bongs from Headshop. Options include Pink Formula.
Alternatively, you can use something like Formula 420, in which case skip the salt. Pour it in and proceed as normal.
Be very conservative with the dish soap. If you use too much, your bong might produce an unpleasant soapy aftertaste the next several times you smoke.
