I'm not sure if you would like some academic literature but here goes:
T’an-luan’s Theory of Two Kinds of Dharma-body as Found in Shinran’s Wago Writings has a detailed description and great diagrams on this topic.
The Dawn of Chinese Pure Land Buddhist Doctrine: Ching-ying Hui-yuan's Commentary on the Visualization Sutra
Nembutsu - repeating a name of a Buddha - is a practice which might help us to
let go of worries,
develop exalted qualities,
and develop concentration.
If you understand and do this practice sincerely, it might bring you benefits even if nobody particularly taught you.
The first effect, helping to drop worries, comes from the ...