The wall is actually a very easy maneuver. While I do it mainly on a larger gas plane, its really no different. The important part is the setup. You need lots of elevator, on the order of 35 degrees or more.

From straight and level flight, at about 1/3 or so normal speed, turn on 3D rates, then pull full up elevator. You want the plane to stop mid air like it hit a 'wall'. There should be very little vertical travel.

From this point, there are many things you can do. Go right into a torque roll, start a harrier, or go into a tail slide.

If you perform a wall on the vertical down line, its called the parachute, as it looks like someone opened a parachute and stopped the planes descent.

For real fun, do the parachute on final approach and end with a harrier landing. Then its called the terminator (I believe because its terminated lots of planes practicing that manuever).

The key is excessive elevator throws. And if you use say 95% or more expo, the plane will be easily controllable from neutral to about 1/2 stick input. This will allow you to recover easily from the maneuver without having to turn off the 3D rates, and the exit from the maneuver will be much smoother.