I have Back2Natural but I haven't been that impressed. I've left it in for 10 minutes and it helped somewhat, but not as much as I was hoping; still had some red/gold tones going on. However, this product is my new best friend:

http://www.sallybeauty.com/Unred-Colo-Dr..._vc=SEARCH


You can add it to Back2Natural or your hair color mixture or even your conditioner. It works like a charm; totally kills red and gives me back that nice brown ashy thing I got.

Re: what Jrob said. Yes, shampooing often will speed up the time that the piece turns brassy. However, I don't really see how guys can go that long w/o shampooing it. If you use any products they need to be washed out, in my opinion. If you just wet the hair the products just stay in the hair and make the hair less than clean and soft feeling. That's just my experience. So I shampoo often and use that unred drabber product.