Greatest bong cleaner I have found is sold at home depot by the gallon. Its called Simple green and washes away residue like its a joke with no issues rinsing. I keep my clear acrylic bongs clean by simply spraying enough of the full strength simple green in there after dumping the rank water and slosh it good in there and most times I do not even need my brush, Rinses away nice, can soak bowls longer if they are really badlol sounds like the old school paper towel tube with the bounty sheets!! before that we just rolled up a bath towel and slowly blow your hit into the towel. Stoners are natural magyvers