Can't really comment on cleaning a Camelbak bladder, but can talk about keeping it clean. I've been using mine for the last 3 years, and only wash the mouthpiece when I get home, just rinsing it in water. I then fill 'er up again and put it in the fridge. Have been doing it for all this time and the water tastes pristine, with no discoloration or gunk floating around or that black liquen that usually forms inside old water bottles.
That is what I have always done. You don't have to keep it full either, just some water in, and in the fridge. Should be fine for years.