There's not really much of a "technique" to it... You point the nose straight up and balance it using the rudder and elevator... If it starts to fall in one direction, correct with the proper amount of rudder or elevator... What makes this fairly difficult is that the torque of the engine will cause the plane to roll... As it's turning you must adjust which control surfaces you are using for which direction.

I had RealFlight G2 for a long time... It was decent, but honestly, for practicing torque rolls, or most other 3D manuevers for that matter, you might as well hang it up. The physics just aren't anywhere where they need to be for practicing 3D... You can learn basic muscle memories, but that's about the extent of it.