Creating enough flip will greatly improve any swingthrough series. The key, more often than not, is in utilizing the full range of the swing, as well as the shoulders to drive the flip even faster. Ideally, landings should be close to upright with only a slight lean. This tends to be the hardest part, at first. If the chest is too low, then swinging the leg through while simultaneously trying to power the upper body to an upright position becomes incredibly inefficient. Once landings are adequately upright, it is the leg itself that does the majority of the work. The leg should swing as far as it possibly can before flexibility forces the rest of the body to come a long for the ride.
Some swingthroughs, such as grandmasters and swings from mega, dont allow for quite as much leg swing, so the difference must be made up with the shoulders. All flips and twists should utilize the shoulders for lift, but the sideways flipping tricks seem to be the most obvious use of this technique. As the leg comes in, the arms and shoulders should throw up high, lifting the body into the air, then pull in and down to accelerate the flip and twist. For all swingthroughs, the key to maximizing the power is to link the swing of the leg with the swing of the arms or shoulders. The two must work in unison; it is crucial that both reach their apex at the same time for maximum power.
Notice the use of the shoulders in each swingthrough. This should be particularly obvious in the aerial to GMS connection at the end. The shoulders drive the chest up (except in the aerial, where they throw downward), setting the point of flip, while the leg swings the hips up and over that point, to create flip.