Advice from Lama Zopa about the long Namgyalma mantra.
The Namgyalma mantra is extremely powerful. If you put this mantra on a mountain, then the whole mountain is blessed and any human beings, animals or insects who touch or climb the mountain have their negative karma of being reborn in lower realms purified just through that. 
If you have this mantra on a banner, even the shadow from the banner purifies the negative karma of being reborn in lower realms of any being it touches.
Similarly, if the mantra is in a house, all beings in the house—not only human beings, but also cats, dogs elephants, dinosaurs, ants, bugs or flies—are purified and liberated from the lower realms.
It is excellent to have many of these mantras in your car, on the inside of the roof. Then, every day people are blessed, purified and liberated from the lower realms.
This is the main mantra for purifying and liberating from the lower realms—purifying negative karma by putting the mantra on the body of a person who has died or chanting it for a person who has died.