yeah boosting your immunity to Acne bacteria is the best long-term solution. also figure out what damages your skin and try to stop it from happening -- they feed on dead and weakened skin. my (incomplete, but encouraging) success against Acne was triggered by showering more often with 3x body wash which has a moisturizing agent. that (I think) left a protective coating and also stopped some of the skin cells from dying as much, letting it recover so it could fight the bacteria better. I know that's not an all-natural solution, but if it works I ain't going to knock it :)
also I've been zapping every so often with the nifty little $10 zapperplans.com model. I really see that as a protection against colds because Acne reinfects so easily. my strategy is to build up immunity to the zit bugs with positive affirmations and healthier skin.