I would add the following four tips to consider as part of the exercise set for more advanced practitioners:
1.) In the first exercise, the right and left hands need to be aligned with the right and left extraordinary channels of the torso as the hands are moving downward. As the hands move up, there can also be a vertical opening of the kwa, or inguinal crease at the hip and groin area. As the hands move down the body, the kwa closes.
2.) Turning at the waist, or kwa, should be a part of exercises 2 and 3, where there is movement to the sides. If you are turning your torso and not twisting it, you will move into the kwa as you move from side to side. The knees should stay stationary, but you will note that the muscles of the thighs will twist. Having someone hold your knees will help you develop awareness of when they move and an awareness as to how much you can move before the knees move. Over time, you will be able to move further into the kwa and the muscles of the upper thigh will twist outwards.
3.) Aim towards performing the movements smoothly, slowly and without any jerky or mechanical-like motions. When first beginning, the movements will be uncoordinated and less fluid, but once you know the moves, this will be the time to work on developing fluidity and continuity.
4.) Breathe naturally and abdominally. The movements are not coordinated with the breath; but even, relaxed breathing with the diaphragm should occur without any holding. If it helps, visualize the breathing as being like a wheel moving, never pausing at the beginning of inhalation or at the beginning of exhalation. If diaphragmatic breathing is something you need to learn, check out Stages in Abdominal Breathing
Many Parkinson's sufferers have reported a reduction in symptoms as a result of taking up qigong practice. Several studies have been summarized on the World Tai Chi and Qigong Day web site. It is one of the many types of diseases that improve due to qigong exercise. A variety of qigong exercise sets, as well as Tai chi styles, can confer these health improvement results. The great benefit of qigong exercises is that simple exercise sets can confer so many health benefits. For those with mobility problems, qigong and t'ai chi can also be done in a chair. A book that illustrates how to do t'ai chi in a chair is shown below. Good instructors will be able to teach how to adapt qigong exercises for those with limited mobility.