Rosemary tea is said to work well.
I tried caffenol with paper last week (I was impatient and wanted to try something). It did work but was very slow and I don't think it achieved maximum black.
I tried Ilford DD-X (a film developer) which is all I had at the time. I found it quicker if I added a bit of washing soda to it Totally un-scientific but it worked.
I think it's a good idea to experiment with paper as if it doesn't work, you have only wasted the paper, not the 'once in a lifetime' latent image which may be on your film.