The answer to this is even easier; stop using shampoo and conditioner, just water. As with many things, it turns out if you stop using the product your body adapts and after a few weeks you don't need it anymore. So far I've ditched shampoo, conditioner, my face care regime (cleanser, toner, moisturiser) and various extra dry skin moisturisers and emollients and deodorant. When I'm ill or stressed the dry skin, BO and greasy yet dry and fuzzy hair return till I get better and then I'm fine again. I know a few people who've converted to this and getting on alright with a reduced shopping bill.
I use soap, it's organic olive oil based, from France with only three ingredients. One bar lasts me and two boys 2months or more so I'm not worried about it causing much harm as can't imagine it building up much in the tank?