Just bought a MTD 535-24 with a maple fingerboard and ash neck - i was blown away by the marvelous B-String, best i got so far BUT i only checked the common dead spots (c-c#) at the store and then after buying it, a heavy dead spot on the D-String around A (Ab and Bb are also lightly affected) ocurred to me. Never heard of this area as a common dead spot but read some replys in this thread with the exact same Note.
I ordered a Fatfinger and hope that it will get better then. Its a pity. This can happen with every bass despite the price or exclusiveness of the luthier. When the Fatfinger wont work i may consider a Drop Tuner (also more mass) - Im unfortunately not a good home worker; So the initial method in this thread seems to be great but i have to find a luthier to do it for me ... ;-)
Fun Fact: Fastest way to check the fingerboard for dead spots is to just play with an octaver. Even at little Dead Spots the Octaver will directly switch to Overtones and you can hear it way more faster than just checking it naturally.