We know how shamatha (calming the mind) or vipassana (developing of insight) practices work but how vajrayana practices work?
All buddhist practices should be about transforming the mind, right?
What exactly we develop through sadhana practices or Protectors practice? Peace of mind? Insight? Its technically the same like with shamatha and vipassana? Or its different?
Is for vajrayana practitioners shamatha and vipassana not sufficient?
Sadhana practice is shamatha and vipassana. However sadhana practice is an extraordinary method to very swiftly (as in within 32 lifetimes) accumulate merit, purify the aggregates and accumulate wisdom. This is done by taking the result (perfect Buddhahood) as the path. The practitioner conceives of themselves and all beings as possessing the fully developed qualities of a Buddha - perfect body, speech, mind, qualities and activities and conceives of the environment as a perfect Pure Land. This is definitely true for the highest category of tantra but is also the case for the lower 3 categories of tantra although basically only during the meditation session (for the lowest category of tantra however one conceives of oneself as a servant of a Buddha).
So as practice progresses over 1, 3, 7, 16 or 32 lifetimes we actualize the profound qualities of a Buddha: perfect lovingkindness, perfect compassion, perfect purity and perfect spiritual power. The highest spiritual power is full and perfect enlightenment.
Protector practice is for clearing obstacles on the path primarily. This is also basically in the Sravaka path with the protector verses and seems to be mostly vestigial in the common Mahayana.
_________________Kirt's Tibetan Translation Notes
"Only you can make your mind beautiful."
HH Chetsang Rinpoche