I cleaned a 1979 Zodiac that was covered with hard to remove dirt, mildew etc. I purchased it in this condition and the tubes now look great. The material is hypalon. I used water and bleach and a scouring pad with an abrasive cleaner like comet and ajax. It may have been a bit agressive but I am pleased with the results.
By the way, is that Chris guy nuts or what?
His post got me laughing anway...