The poisons that work for other spiders will not work on fiddlebacks. As Dennis pointed out, the glue traps work best. We have a buttload of the nasty critters out here. The glue boards don't get them all, but they do cut down on them (scorpions too).
I agree. Had a nasty infestation of them in a house we used to live in, and the pest control guy said they are hard to control, as the poison has to actually be on their body; he said they don't clean themselves like roaches or other instects do, and they walk with their body so far off of the surface that the poison may get on thier feet, but never really makes it into their system. He used a dust called "Delta Dust" (very fine and settles on their bodies, wherever they may be hiding), and after that I started buying it online and "blowing" it in the attic with one of those hand-crank, garden dust blowers. I also put very sparing amounts of it around the baseboards where there was carpet. Seemed to help, but never did get rid of them.