Now you put it in a way, which makes sense to me. I can only tell my experience:
I met my spiritual twin (if this really is what is meant by nahuali), which was human. I did merge with her (had the feeling not knowing which one I was). She is also strong healer. She is real, not only at spiritual form. If I have the concept of nahuali right, obvioisly you have to find it first, before trying to merge with it. I am not sure about becoming it, what it would be.
Then I have my poweranimal, with whom I work when joyrneing. I use his pover and other poweranimals', also client's when doing healing. Foremost I just let things happen during healins sessions naturally, whatever may happen.
Wikipedia offers something about lucid dreaming, also basic tehcniques into it.
Have patience, spirits/gods have come into your dreams and teach you. If you 'burn' with the must have vision, go and get it. Do fasting, pray, be at solitude, whatever it takes. Joyrneying to your god is also an option. You may joyrney for the teaching also, it may prove better than learned from books or a person in this world.