The visualization you mentioned is the standard visualization across all the schools of Tibetan Buddhism (although even that has some slight differences from lineage to lineage). If you can go back and ask the geshe for the Vajrasattva mantra you should use however in the Geluk tradition the standard order seems to be: Su-tuṣyo me bhava, supuṣyo me bhava, anu-rakto me bhava and has ah hung phey at the end.
Regarding the "ah hung phey", this is what I have learned (from http://www.visiblemantra.org/vajrasattva.html
The basic mantra ends with āḥ. Hūṃ and phaṭ are traditionally added under specific circumstances - hūṃ when the mantra is recited for the benefit of someone dead, and the phaṭ when the mantra is recited to subdue demons.
I take it that hung = hūṃ, phey = phaṭ?
The version with Su-tuṣyo me bhava, anu-rakto me bhava, supuṣyo me bhava is the standard Sakya order but there are two versions of the Vajrasattva mantra in Sakya and I always have to pay attention to the order in the common Vajrasattva mantra because actually the common Vajrasattva mantra is not the the one usually recited. This order ( Su-tuṣyo ... anu-rakto ... supuṣyo) can also be found in Nyingma sadhana although the more typical order is Su-tuṣyo ... supuṣyo ... anu-rakto) with just ah at the end.
When you wrote "Sakya order" did you mean the Sakya Trizin?
However Vajrasattva is the same purification Buddha and the same mind shrine and you will have the same blessings no matter the order of the su-tusyo ... supusyo ...anu-rakto .... Yje Sanskrit is a prayer to be blessed by Vajrasattva, to become totally pure, to receive his siddhis and to become just like him in every way. The practice operates on the power of the shrine (the visualized Vajrasattva being nondual with the real Vajrasattva), the power of regret (regretting all the downfalls one has created), the power of the antidote (resolving to not repeat the downfalls) and the power of restoration (faith that the meditation has purified oneself)..
Taken from the Ewam Choden
note on this point:
Vajrasattva sitting on top of one’s head is the power of shrine: the power of the deity on whom one depends. Through him one can be puriﬁed. Producing a mind which strongly regrets all sins previously accumulated is the power of regret, of overpowering. The thought of never performing sinful actions again, from this time forth, even at the cost of one’s life, is the power of the antidote. Strongly believing that this meditation will completely purify one’s mental and physical obscurations is the power of restoration.
Thank you for your informative answer on the order of the phrases!
Your phrase "to become like just like him[i.e., Vajrasattva] in every way" struck a chord with me. Since my practice of the 100 Syllable Mantra for purification and reading about Vajrasattva, I discovered that I probably have a fair bit of affinity with him. I didn't realise this in the past. The two main Buddhist practices I had already chosen were the Casket Seal Dharani and contemplation of buddha. According to the sutras these two practices are practised and upheld respectively by the two bodhisattvas Vajrapāṇi and Mahāsthāmaprāpta. Both are, as I've recently found out, the same deity as Vajrasattva.
As a side note, with the story of Vajrapāṇi Bodhisattva and the Shaolin martial monks, this may possibly be a linkage with my passion and practice in martial arts too.
I wonder where I can read more about Vajrasattva, so that I can learn to be more like him. Suggestions welcomed!
Kirtu, does this name of yours have any relation with Vimalakirtu?