I just started teaching Cyrus this couple weeks ago, with my RI, we started with turns on the forehand before Xmas though and once he was doing those well we started leg yielding.
The turns on forehand really helped him get used to moving off my leg on both reins properly so was good foundation for leg yielding.
For leg yielding break it down into steps of each aid you have to give and start doing off just doing it in walk. Big pats if he does it right. Helpful to have someone on the ground watching to make sure back end isn't swinging out and stuff like that.