Antti,
The figure-8 does feel strange, in my experience.  It took awhile before I got used to the movement.

It sounds like you have tried several different slinging styles.  When I started slinging, I also tried several styles before trying the figure-8 (or Weaver, or Nwmanitou, or Spencer) overhand.  I started out with underhand, more like Mgreenfield does it than David Taylor's Greek underhand.  I think this was one of the reasons I had problems with the figure-8.

The final snap of the figure-8 is very fast.  The sling accelerates incredibly, as it comes up and over your head, and if your reflexes are accustomed to a "slower" style, you will release late and send your ammo straight into the ground in front of you.  That's the way it was for me, anyway, and several other people offered anecdotes that match.  One person even suggested wearing protective gear to protect one's potential children from harm.  He had apparently released so late that the sling pocket (and contents) nearly struck him.

The only advice I can offer, is that which was offered to me: keep trying the figure-8, and it will come to you.  Probably suddenly.  It is like your reflexes are busy reprogramming themselves, and nothing works until the job is done, and then suddenly it is easy.  That also was my experience.

Tint's suggestion of bending backward (that is, away from the direction of throw) like you were throwing a  javelin, is a good one.  That is what I do when I am slinging for distance. If you are right-handed, you will actually be bending to your right, since you stand cross-wise to your target (line from target passes through left shoulder, then right shoulder).

Just watch some videos of proffesional tennis serves... they're really quite amazing.

I believe that the Figure Eight has a huge potential for power. There aren't very many slingers anymore, and so we haven't refined the process very well. However, tennis being a major sport means that thousands upon thousands have tried to find better ways. So far, the figure-8 tennis serve is the most efficient way to get a tennis ball in a square box with a LOT of power (over 150 mph. for Roddick).... Of course, this is tweaked since power is not the only variable, the advantage of a high contact point helps for tennis....

Ok, anyway....
My most powerful and longest casts come from a figure eight. With techniques such as underhand/sidearm (typically recognized as best for range), you are getting most of your power from your arm, with some coming from twisting your body, and a bit from your legs.
However, with a figure-8 you can coil your entire body as one enormous spring. Legs (including calfs, and humans' specialized achiles tendon), back, and abs can rocket up, while your body twists, and all arm muscles are used. The wrist can have a much larger role in a figure 8 than, say, an underhand as well. Indeed, a serving motion can be powerful enough to break your own back... as happened to my friend.

While I'm not doubting it's effectiveness, I don't think that the skipping windup for the figure-8 depicted in one of the videos is the most efficient means of using this cast. A tennis serve approach is probably better.

As far as the difficulty is concerned. I assume that it's a lot easier for tennis players. However, I was introducing slinging to a friend (never played tennis), and I showed him the figure-8 first. After a couple close calls to my head, he got the hang of it and was slinging well over 100 yds (it was into a pond, and all that I knew for sure is that it was definitely way further than a football field)  - And he was really only using a basic cast, just arm and torsion.


Another thing which sucks power from these casts is pausing once your arm is behind your back... Don't Stop! Bringing me to:
A note on how the figure eight is different than a tennis serve (just one aspect that is). In tennis, the motion is relativly slow, with the punch being added only as the raquet begins going up, to meet the ball. I think that with a sling, it would be more efficient to start the extra kick when your arm is behind your back. Bear with me here, it's hard to explain:
Your feet are close together... see a tennis serve to know what I mean.
Right after your arm comes behind your head, snap it down with your biceps and wrist; as if you are touching the back of your thumb to the shoulder of the slinging arm. This motion should coincide with the rest of the body's drop into a coiled and very tense stance... Lot's of power waiting to get out. In tennis, the arm and wrists rapid movement a this point isn't very efficient, since it's hard to rechannel. However, on a sling it's perfect.
Once back, swing forward as though it were an apache style cast - the difference is that your elbow is out to the side of your body and slightly behind it. Simultaneously lurch forward with every muscle, going up and twisting. Snap your wrist... extend everything, and follow through.

Just get out and watch some videos of the tennis pros serving. In their windup they get WAY down... much further than the videos of the slinging style. I think that we can learn a lot from them. And its far easier to see than it is for me to explain. Like most things, it's just psychological. When I get into it, I can sling much harder than with any other style... no comparison really.

Yesterday I decided to try figure-8 again, and I have a guoestion:

Which way is the palm supposed to be facing in the end of the throw (when you release)? With me the palm is facing up, is that wrong?

cant tell from the videos, they are too fast..

However, I noticed, that figure 8 is better for my shoulder than apache.. Apache feels in the part of my shoulder, which I injured last year, but figure 8 feels in a different place, which is good.

Thanks Dale.

Good idea to look those videos frame-by-frame.

I think I am finally getting the form right. Havent ever gotten stones as far. 60-70m (my estimate). Cool. The only drawback is that my accuracy has suffered a lot compared to apache.

If the palm is down or left, I get more power than if the palm is up. (interesting..)

The tennis serve pictures were also really helpful..