I find this kind of thing easier to do when I am actually in the room with the guitarist and his collection of weirdly tuned guitars, and I can pick up where the root notes are in the hand shapes by ear/sight. And, yeah, it hard to find straight chord charts for open tuning songs, and there is a reason for that.
Listening to the recording and transcribing is the most straightforward solution. Also, if you got an acoustic guitar lying around (which I'm sure you do) you can tune it to the open tunings and find the root notes in the tab, transpose them to your bass - I've done that before, probably with a Black Crowes tune.
Listening to the recording and transcribing is the most straightforward solution. Also, if you got an acoustic guitar lying around (which I'm sure you do) you can tune it to the open tunings and find the root notes in the tab, transpose them to your bass - I've done that before, probably with a Black Crowes tune.