Darkgreen, I've never really analyzed what I actually do. I actually transition between a two-finger stacked grip to a power-grip during the hit. However, I will not recommend anyone doing this as I'm sure this can compound any wrist-roll that you might have. It's just a natural motion that works for me.
Now for my wrist motion which might be of help to you. This is more of a palm-up karate chop that has a lot of flexibility in the wrist. My wrist goes from open to closed very quickly at the hit. The best way for me to describe this is to grab a disc in whatever grip feels comfortable to you and rotate the disc so that the top of the flight plate is facing left (assuming RH) and the disc being perpendicular to the ground. Now, open your wrist like you were trying to hit the top of your forearm with the edge of the disc and then rapidly closing your wrist, trying to hit the bottom of your forearm. This is the motion that happens at the hit. The faster that this happens and the amount of travel between your wrist being open and closed will result in longer and more stable disc flights. I try to keep my palm facing up as long as possible throughout the entire throw.
Imparting spin on the disc (what I just described in the wrist motion) is the key to distance with a FH. The more flexible, smooth, quick and amount of travel this motion is, the longer the disc will stay in the air before fading out. If you try to muscle the disc (just using your arm without any wrist movement), you will not impart any real spin on the disc causing it to either turn-and-burn or fade-off very quickly.
Without a run-up or a backswing, I can push discs out to about 200'. Every type of disc requires adjustments to your throw to find the balance between speed, spin, how much (if any) run-up and backswing. Just like backhand, you want to feel as you did nothing at all to make the disc fly. Smooth and quick without force.
"Imagination is more important than knowledge" - Albert Einstein