Hello Hendrik:
Hypnosis can go for internal spiritual or external worldly purposes -- usually the latter in our present cultural situation, though it seems to be changing for the better. For more comments on this, see my note of Oct 6th in
this topic.
Regarding the cultivation of "sex magnetism" and "personal magnetism" for their own sake, this approach will be a distraction from yoga. Paradoxically, the more we focus on inner development and the less on "powers" such as these, the more we will gain them. This will be in the right direction, because then these natural abilities will come up in support of our increasing inclination for service to others, rather than an egoic manipulation of power, which always leads to more bondage.
More focus on spiritual development = more service to others, more powers in support of that and more freedom.
More focus on development of powers = less spiritual development, less service to others and more bondage.
In a nutshell, that is the case against developing powers (siddhis) for their own sake. So, I do not agree that power should be "directed." Power is a by-product of spiritual development -- not causative at all. If we make the mistake of thinking we are in charge of power as a cause for good, we will end up with less, not more, and so will those we influence in that way. Inner silence (pure bliss consciousness) is the cause of all good and all power.
"Seek first the kingdom of God and all will be added to you."
So the advice is, become firmly established in a routine of daily deep meditation, and then do the other practices (spinal breathing, asanas, mudras, bandhas, samyama, tantric sexual methods, etc.) that cultivate our nervous system as a pure channel for outpouring divine love (divine power). Then things will be in the right order, with the best results for all concerned.
The guru is in you.