A fast soul is pretty much the same as
the back slide, with two minor
differences. The first, and obvious one,
is that your sliding foot is doing a soul
slide on the rail. The second difference
is that you don't need to turn your body
perpendicular to the rail to soul. You
can just keep going straight ahead and
it'll work fine.
Being able to do soul grinds is of great
assistance when trying to learn this
trick because being able to lock in the
soul foot is a skill that takes a bit of
practice to acquire. In any case, you
approach the rail just like you are going
to do a soul grind. Make sure you jump
up high and get your weight on top of
the rail. Lock in the soul foot and away
you go. The free foot can be doing any
number of things,
but a typical action is for it to be either
grabbed by a free hand or placed next
to the souling foot. Soul like normal and
hop off of the rail. The beauty of this
trick is that it is an easy extension to
soul grinds because a proper soul grind
has almost no weight on the lead foot.
And since little weight is placed on the
lead foot, it is easy to take it off. The
only hard adjustment to make is
balance. For many, the lead foot acts
as a rudder and guides you down the
rail. However after a bit of practice it
becomes easier.
So remember to jump high, get your
weight over the rail, lock in the soul foot
solid, and ride it out.. Good luck, and
remember no rail is too long!