The evil grain needs a lot less agitation. All your tests were constant agitation which explains the constant grain results.
Stand development will get you the finest grain (no agitation) but can suffer from bromide drag and low contrast. What rodinal loves is gentle periodic agitation, like a gentle swish you would give a fine wine. Somewhere between stand and 1 minute cycles with only about 5 seconds in duration. Agitate more often for greater contrast and less for minimal grain. It's a balance.