In my experience in taming you will need

#1: fishes in baskets (0.7x up)

#2: gilly armor (optional)

#3: skill (you will most likely die)

#4: spy glass

Step by step to tame :

1: locate desired shadowmane

2: wait for nap time (day)

3: approach for the back (away from face!!)

4: feed fish

5: RUN

6: wait for hunt to end while watching with spy glass

7: repeat