Rodinal has all kinds of myths about it on the internet spread by people who don't really have experience making prints. I agree with NB23 and Ian. Stand development is a bad way to develop film, especially if you going to print it the traditional way. You can do just about anything if you are scanning it however, which is how I think these myths get promulgated. People make all kinds of claims on the internet to feel special about themselves. Tri-X at 64,000! for example. Never gonna happen unless you operate under a different set of physics than a mortal man.

Kevin, if you already have Rodinal and want finer grain while using it, I know of two ways (there are surely others): Salt and Sodium Sulfite. I have never tried the Sulfite, but I do use salt occasionally. Use sea salt or table salt without the iodine. 30g/l will do it. I have read that salt may cause dichroic fogging with modern films, but I haven't experienced it yet. You may also lose some film speed with the salt FYI since from what I understand the salt acts as a restrainer. Maybe Ian can shed some light on that. Salt is a good option for you to try since it is easy to get and it works. Good luck.