My experience, hope it helps:
I do pray a lot and the best prayers for the benefit of others can certainly have a noticeable, positive effect upon you (you get what you give). "I am praying for the enlightenment of all beings" is a good one. But the important bit is that you mean it, put a bit of intent/energy/will into it, or it's just words. I suppose that the same prayer said over and over is chanting to an extent, but I make no claim to have any specific knowledge of chanting as a practice. I "chain pray" because it helps me, and knowing that it helps me, I know that it is helping others.
I don't pray out loud, I intone the words in my mind along with the in and out breath through the nose. It is easy to become distracted by the wandering mind, and the underlying prayer can become flat and one-dimensional, losing efficacy until attention is restored to it.
Peace...
