I've got a great tip if you've got a giant glass-on-glass bong that's barely possible to clear, such as a large beaker base like mine. This could apply to a lot of g-on-g bongs though.
Tip:
Before you light up,
push and slightly twist the bowl and the diffuser to make a better grip (but
NOT too hard, just what feels safe). Then slide the diffuser back in, but don't tighten it, let it rest as it falls.
Light up, do what you do, and
when it's all milky, pull out the diffuser. But you don't have to pull it out all the way and risk breaking it, just above the joint should allow plenty of air to clear it.
This minimizes unnecessary drag when clearing it, because the air replacing the smoke surely doesn't need cooled through water, unless you're in Hell...
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And here's just a vid of this crazy piece I have, you may have seen another thread a few weeks ago about it, added an 18.8 ashcatcher to it ;]