Toning with tea is a nifty trick, I've found that cheap-o tea tones better, since it has darker color and less flavor compounds.
Tea actually stains the paper, and I believe that the tannins interact with the silver compounds.

A while back (sometime in the early 90s) I did some tea stained prints (light yellow stained, not too dark) that were still good after 10+ years on display at my mom's house.

IIRC i used 4 or 5 bags of tea in a liter of water to obtain a very dark infusion, let it cool down and inmerse the prints into it. After that a short wash in running water was all they needed.
I have tested it on both FB and RC papers, generally the FB papers will take the stain better, but the Ilfospeed and Fortespeed did take it a lot slower.