I'm sure we all eventually have to deal with the gold/red undertones after a few months of wearing. How do you guys deal with it?

I'd like to use back2natural on my black unit, however, they do not seem to have an option for black hair. Are there similar products for folks with black hair? I've found a product which appears to be similar and claims to work on black or brown hair, called PPI Color Correcting Red Shampoo...have any of you tried that?