Thank you for all replies to my questions.
The Zer Nga practice sounds interesting, but I don't know if it is the same as the practice I mentioned, which is a common sutric practice as far as I know. I'll try to study the Zernga booklet.
When reading in the ChNN Guru Yoga book about the method for recognizing rigpa through the experience of emptiness I just thought it was the same principle as the death contemplation.

