Just to get back to the original subject (Rodinal Special)...
I swear by Rodinal, but for films up to 100 ASA. I mostly use Efke KB-100 (35mm format) and R100 (medium format), and Rodinal 1:50 at about 10-11 minutes yields absolutely excellent results.
However, for 400 ASA films (I use TMax400 shot at EI 400), the grain often gets very visible.
In trying to find a suitable (liquid) developer, I got some Rodinal Special (readily available here), but was not happy with the very short dev. times at recommended dilution. I ended up with 1+50 dilution and 14 minutes dev. time for TMax 400 with acceptable results and smaller grain than (ordinary) Rodinal.
I was not very successful in finding online recommendations for Rodinal Special (or Studional, same thing) at higher dilutions, so I used trial and error to arrive at 1+50 dilution and 14:00 minutes at 20 deg. Celsius.
For TMax 400 I find that HC-110 (dilution "H", i.e. 1+19) also produces good results, but it's also more expensive than Rodinal Special.
Still, I'll have to do some more testing with Rodinal Special. And yes, with 1+50 dilution, I use it as one-shot developer.
As you might have noticed, I prefer liquid developers and avoid mixing powders... Still, I'll have to try that 5-liter pack of powdered Xtol I got recently. I'm told that it's excellent for TMax 400, even pushed to EI 1600!
As for "High Church of Rodinal", you could say that I'm an ardent follower

Nothing beats Efke R100 souped in Rodinal. Sharp and crisp!
Regards,
Denis