I didn't read all the suggestions in this thread, but I want to mention this:
I bought a daypack for hiking from walmart and it has a refillable bladder inside. Company is Outdoor Products. They also sell a cleaning kit for the bladder and hose. I found the best brush for cleaning my blowoff tubes in it.
It's a scrub brush that's about two feet long and made out of a spring. It's completely flexible and is perfect for cleaning all the dried krausen from inside the tube.
Not sure if that's been suggested already, but that brush is one of the best brushes in my arsenal and the only one capable of scrubbing the inside of my hoses 100%.
It looks similar to this version, but with shorter black bristles: