Instead of trying various things to make Rodinal behave in an uncharacteristic way, why not just use a fine grain developer to start with. When you modify Rodinal it ceases to be Rodinal and the properties that people are so intent on retaining are lost.
Now why didn't I say something brilliant like that? Oh, I did. Agreed. But since I enrolled on here, I came to note that Rodinal has its fans. Some things defy understanding.