Nembutsu - repeating a name of a Buddha - is a practice which might help us to
- let go of worries,
- abandon self-centeredness,
- 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 fact that people usually live in a lot of insecurity. Practising nembutsu, they don't need to rely on their weak skills anymore, they rely on Buddha. So they find a ground to feel well and secure.
The second effect, abandoning self-centeredness, results from the same change of perspective. Rather than relying to ourselves, worrying about ourselves etc., we might wish to become selfless. Nembutsu practice can constantly remind us about that, so we change our mental habits from being self-centered to a selfless view.
The third effect, developing exalted qualities, comes from concentration on qualities of Buddha, such as the wisdom of clear seeing, calmness, compassion etc. Concentration on such qualities helps them to grow in our mind and around us.
The fourth effect, developing concentration, actually reinforces our mastery of the mind, feelings of strength and security. I didn't practice nembutsu very much, just a couple of months, but I noticed that through that practice my personality became more direct and self-confident. That was an effect of chanting "námó dìzàng wáng púsà" or reciting "Kshitigarbha" (I tried both approaches) 1000 times a day. When you are walking down the street or riding a bus, regardless of other people looking at you etc., you naturally develop perseverance, confidence, and drop imaginary barriers between yourself and others.
Thus this practice can work well, and might help you to come closer to awakening.
Different people have different situations and affinities, so it's hardly possible to say in advance, how well the practice will work for you. To see the effects of practices, we should try them and directly observe our experience.
Chinese Chan (Zen) teachers might say that they use mantras and nembutsu in a different way, not like in Pure Land school. Not for reliance on Buddhas but just for developing concentration. As Buddhas are projections of the mind, why not work with the mind directly? So in Zen it's rather a supplementary practice than the main one.
Nembutsu practitioners might be criticized, because in place of attachment to self they might develop attachment to nembutsu, or to their fantasies about Buddhas, to images of Buddhas, to pleasant feelings of deep concentration etc.
Therefore, it might be recommended to keep wide awareness of your experience as a whole, rather than just immersing in chanting and forgetting everything around. The purpose of Buddhist practice is not to escape from this world but to transform our experience remaining in the midst of life.
If we overdo developing concentration-tranquility, and neglect awareness, that might develop dullness, "lazy mind", not conductive to good practice. And the opposite, developing awareness without tranquility might lead to exhaustion, because as our concentration grows, vexation also might become stronger.
So if you explore the practice of nembutsu, it's best if you keep the balance of tranquility and inquisitiveness, and keep wide awareness in order to avoid developing attachments. To let go of attachments, it's advisable to practise active helping others, Six paramitas.