Ok! I got a chance to try this method to compare to the direct toning in tea that I mentioned above - so time to report back.
I tried several combinations, always pre-soaking the print and then washing between solutions - Bleach -> Tannic Acid -> gave a nice dark blue-black tone - not the sepia brown. (I, too, mixed my own chemistry).
TA -> B - gave a pinkish purple tone that I really didn't like.
B -> TA -> B -> TA - yes, I went back and forth and got a bit of a dark mageta tone - but the paper was starting to get heavily stained.
I was trying to get more punch in the whites compared to direct tea toning - i.e. less staining and more of a toning. But thus far the highlights don't look to be any whiter than direct tea toning. But you definitely have a wider palette of tones. What I did like was the rich blue-black tone you get immediately after putting the print in the bleach - before the print fades. But I'll have to try it with some overprinted samples later.
To Gandolfi (and others) - any comments on this bleach only procedure will be appreciated. How do you stop the print from fading beyond a point. Does the alkaline bleach only procedure make it non-archival - how are your bleach only prints holding up?