I will jump in here and comment on the OPs original concerns and say that if you want an easy to use solution that will get you deep black color look no farther than Mark Lees express blue. In my opinion, once you use it, you wont want to use anything else.

A set of barrels can be done in 4-5 hours. That is start to finish. The boiling tank never cools down. And that is with running around 8 cycles.

But if you want to do it old fashioned and mix your own, then the above is not for you.

B.Dudley