Flowerpot, I don't know of a specific prayer which is the only one, and I'm not sure that the word "levels" truly expresses what we experience in the afterlife. My understanding is that we are free beings who can "ascend" to any state of being in this life and the next, depending on how well we can open up to love and light in our hearts. This is a skill we develop. That's the best explanation I can come up with. But, I also believe that we have helpers nearby, wherever we are, and that our love reaches all those we care about, wherever they are. So, your love and encouragement is already felt by your loved one. It is immediately part of all that is, and reaches its destination, although destination is a word, and words have limitations. However, certain prayers are a medium which people can use, if they choose to do it. You can say: Nam Myoho Renge Kyo, if you would like to use that one, and think of your loved one in a loving way. This chant, said over and over as desired, speaks to the highest "level" of consciousness that we possess as human beings. But, that is only one way. There are countless ways. Your intention is what matters, what is in your heart. So, however you pray, however you hope, it is heard.