I can't answer your question but I use baby shampoo on my brushes and I think it cleans even better than the MAC brush cleanser. I've tried both and I have to say it's better and more economical to buy the baby shampoo. I've also used face wash (it was the clear yellow Neutrogena kind) on my brushes successfully!
I use baby shampoo too, for now. But I wanted to have something to clean my brushes (especially my 190) a little bit more often, or is that possible too with baby shampoo (like cleaning them two times a week)?
Yeah I don't see why not! If you can wash baby's hair with it I would think it should be fine on brushes. I use it all the time and haven't had any problems yet! I do make sure to rinse them really well though because it seems to make a little more suds than the MAC brush cleanser did.