While wooly buggers receive all the hype, these "cat flies" are a useful variation to fish as a team or singularly.
Tassie fishing guide Bill Beck on his Krystal Cat fly...
This fly is used in my 3 team rig and is attached on the middle dropper. The positioning of these flies is not set in concrete but, over many seasons of guiding, the positions I have recommended have proven the most reliable. Best fished using the Scientific Anglers Mastery Wet Tip in sink rate V with the Green machine on point and Lurex cat as top dropper. Best fished from drifting boat using a drogue to control the speed of drift. Vary your retrieve rate from short sharp pulls to long slow retrieves until you find a speed the trout like on the day. Also, mix up the depth fished from starting the retrieve as soon as the flies hit the water to counting down in multiples of 5 until the depth the fish are hanging in has been found.