Gyaltsen Tashi wrote:
Aren't there simple practices like Chenrezig (mani recitation) and Guru Rinpoche (7-line prayer and Vajra Guru mantra) that can bring the practitioner to Buddhahood in one lifetime?
If you do Vajra Guru and 7 line prayer with strong devotion a perseverance, then you will without any doubt meet with Guru Padmasambhava and he will become your teacher. So in the end, yes it can be a base for attaining Budhahood in lifetime. I don´t know about mani, but Vajra guru mantra for sure has this effect.