Here are the GPX files for both the original DBBB as I understand it, as well as a much easier version I've done. The files should work on Gaia and on pretty much any Garmin GPS.
The DBBB itself doesn't go to the Nada Tunnel, which is a crime, but you should definitely check it out.
There should be waypoints included with the main DBBB GPX. That includes the giant rock that's been discussed here, a large mud pit at the end of Spaas Creek Rd, and gas, food, camping, etc. I forget who I got this from, but the credit is not mine for the most part (I added the rock and mud pit).
The very west end of the DBBB loop is where you go through what feels like someone's property/driveway, but is in fact a public road. He's got a gate across the road that should be open. I've never been harassed by anyone there other than a dog that likes to chase.
The last part of the file is a segment labelled "Hard 11" and is part of the KY Adventure Tour and overlaps some with the DBBB. The easy route uses a few parts of the DBBB, some of the KAT, and some of my own routing. The Hard 11 alternate route avoids the giant rock by turning just beforehand onto Walker Creek Rd. Again, it's not a super easy route on it's own, but it shouldn't wreck your trucks.
I'll keep you posted on what my plans are for next weekend.
GPX viewer
GPX viewer