This is the closest I've ever come to the DB sound. LaBella black tape wound strings on a Rob Allen MB-2 and a Deep 4.
Nothing odd or unusual here. I had used TI Acousticores for years, but they sound more like a model of a DB, with the freaky low tension giving the strings an exaggerated mwahh, and the big upper mids and highs. The LaBellas are more work, but they get fat bass and detailed mids through the undersaddle piezos. Smooth bloom, controllable mwahhh, and a rolled off high end that doesn't require much work, if any.
These basses have hard lined fretless boards and bridges, simple but well-executed undersaddle piezo pickups, and lightweight bodies. Rich, vocal tones. If I knew how to post soundclips you could hear what they sound like.
There is a ton of technique involved, for sure. You can get a friendly DB-like tone out of a lot of fretted electrics if you practice enough!