All done to death I know, but nobody flies NDB procedures with the ADF. The bearing error, especially at a coastal location, can be 20-30 degrees off, so it actually proves zilch.
I have an RMI which makes them theoretically as easy as the VOR equivalents but it still doesn't result in any accuracy.
One flies them using the GPS, in OBS mode usually.
I know one has to carry an ADF, because so many IAPs still involve an NDB, but that is a different issue from banging NDB holds and approaches using it.