Right, so start getting him used to you extending his wings. Praise and treats are key. At the same time get him used to putting his head thru the head stall part of the harness. First hold the treat just a Lil bit on his side, and every session make him reach further and further into it , until he actually puts his head thru. Use the ON command to put it ln, a treat and then the OFF command to take his head out, and then a treat for that too. Be consistant, that's very important. After he is comfy putting his head thru, next step is to lay the harness over his body, very loosely adjusted. Once he is OK with that, it's a matter of tightening it up a tiny bit each session. Yoshi may take to it like a champ, or he could be like salty, and we are at it at least 6 months and not done yet.
Do this session every nite without fail. I combine it with lots and lots of trick training, every nite. YSA are very smart, and love doing tricks. Salty does
Turn in circle
Roll over
Step up on chop sticks
Put small balls into a cup
Walks thru a big hoop back and forth
Puts colored rings on appropriate posts
Plays xylophone
Shakes hands
Learning to distinguish different animals
And Harness training
So Yoshida can be trained to do a lot!
. I did get some pistachios in shell roasted not salted and a variety of nuts in shell. 
