Among the other washes that Affliction does, the predominant one is a mineral wash.
This consists of putting your dyed t-shirts into an industrial dye machine that has been filled with small foam blocks and has had Potassium Permanganate added to the bath. It gets run for anywhere between 3 - 8 minutes depending on how much of the effect you want. It gets neutralized in another bath so that all the acid gets washed out.
I suggest that if you're going to do this you not do it at home. I don't think you'll get the same effect that you're going after.
Also, keep in mind that the dye base that you use to dye the actual T prior to mineral washing is important to the end product also.
John