clothes washing powder is the best i've found. A 2kilo box'll last you months of cleaning after every sesh for about $3. Just put a few teaspoons in ur bong, top up with hot water, let it sit for a minute and watch the resin bubble off... Try it, you'll be amazed... Those bong cleaners you get in headshops are the biggest rip off, you just paying for the words 'bong cleaner'!