I tried Clump (it has to be all along the length) along long hair with lots(!) of subdivision (100+) then Kink and or Frizz like crazy – values from 30 to 100% with scales up to 5000 and got sort of dreads but I could never get it organized enough, it was too frizzed.
The other possibility is to ‘model’ the dreads, extrude (Matrix) them out and use cloth to make them drape then add a material or Hair.