Stay away from the FF 3... it's no good for dreads. If you're going to use a FF product, go with the FF 6. Better yet, use Kryolan or Burman foams. I've used them all and am convinced that the Kryolan is the way to go. Steve is having good luck with the Burman (my results with it varried too much for my liking). The FF 6 is pretty reliable and gives fairly good results, and doesn't seem to be as finicky as the Kryolan, but you won't get the same results.
Brian